2022 Solved Old Paper (BOT-102)

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Rhizoids versus Scales:-

Unicellular rhizoids arise from the lower surface of the thallus which may be smooth or tuberculated. The scales are multicellular, violet coloured and single cell thick.

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Apospory:- It is the development of 2n gametophytes, without meiosis and spores, from vegetative, or nonreproductive, cells of the sporophyte.

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Hornwort:- Anthoceros is also called as hornwort. The common name refers to the elongated horn-like structure, which is the sporophyte.

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Gemma Cup (गेमा कप):-

> On the dorsal surface along the midrib, there appears a cup-like structure known as gemma cup. It appears when the thallus attains maturity.

(पृष्ठीय सतह पर मध्यशिरा के साथ एक कप जैसी संरचना दिखाई देती है जिसे गेम्मा कप कहा जाता है। यह तब प्रकट होता है जब थैलस परिपक्वता प्राप्त कर लेता है।)

> Marchantia also reproduces by formation of multicellular bodies called the gemma. 

(Marchantia गेम्मा नामक बहुकोशिकीय पिंडों के निर्माण द्वारा भी जनन करता है।)

> Gemmae are produced in large numbers within a small cup-like structure called gemma cups borne on the dorsal surface of the gametophyte along the midrib. 

(गेम्मा एक छोटे कप जैसी संरचना के भीतर बड़ी संख्या में पैदा होते हैं जिन्हें गेम्मा कप कहा जाता है जो मध्यशिरा के साथ युग्मकोदभिद की पृष्ठीय सतह पर उत्पन्न होते हैं।)

> Each gemma after detachment from the gemma cup germinates into a new plant under favourable condition.

(गेम्मा कप से अलग होने के बाद प्रत्येक गेम्मा अनुकूल परिस्थिति में एक नए पौधे के रूप में अंकुरित होता है।)

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Apomixis:- When embryo is produced from the parent plant without fertilization, it is called asexual reproduction. Any vegetative cell acts as a zygote. The resulting seedlings are clones of their parents. It is of three types -

i. Adventive Embryony

ii. Apospory

iii. Diplospory

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Species of Rhynia:- The genus is named after the locality and possess two species: 

i. Rhynia gwynne vaughani 

ii. Rhynia major 

> R. major & R. gwynne vaughani were herbaceous plants. 

> R. major was larger than R. gwynne vaughani.

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Telome concept:-

Telomes:-

> The name telome has been given to the simple ultimate terminal portions of dichotomously branched axis. 

> These axes are undifferentiated and single nerved. 

> Two telomes of a dichotomizing axis are united below the point of dichotomy to form a fused structure, called mesome. 

> There are two types of telomes on the basis of their function:

i. Vegetative or sterile telomes:- These telomes are without sporangia and they are also called phylloids. 

ii. Fertile telomes:- Those telomes which bore terminal sporangia are called fertile telomes. 

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 Stele of Equisetum:- 

- Beneath the endodermis lie the stele. 

- Stele is dissected siphonostele. 

- Vascular bundles are arranged in ring. 

- Each bundle has three small strands of xylem between which lies the phloem strands. 

- The centre is occupied by a hollow pith containing water.

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Horsetail:- Equisetum is known as horsetail because they resembled a tail of a horse.

Horsetail plant

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Smallest Bryophyte:- Zoopsis is the smallest bryophyte (5 mm.)

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Origin of Bryophytes (including fossil record) ब्रायोफाइट्स की उत्पत्ति (जीवाश्म रिकॉर्ड सहित):-

> Bryophytes are small, non vascular land plants, that require water for reproduction. 

(ब्रायोफाइट्स छोटे, असंवहनी स्थलीय पौधे हैं, जिन्हें जनन के लिए जल की आवश्यकता होती है।)

> The defining features of bryophytes are that their life cycle featuring alternating haploid and diploid generations with a dominant, branched gametophyte stage. 

(ब्रायोफाइट्स की परिभाषित विशेषताएं यह हैं कि उनके जीवन चक्र में एक प्रभावी, शाखित युग्मकोदभिद पीढ़ी के साथ एकांतरित अगुणित और द्विगुणित पीढ़ियाँ शामिल होती हैं।)

> The term "bryophyte” has its origin in the Greek language, referring to plants that swell upon hydration.

("ब्रायोफाइट" शब्द की उत्पत्ति ग्रीक भाषा से हुई है, जो उन पौधों को संदर्भित करता है जो जलयोजन पर फूल जाते हैं।)

> The bryophytes are quite soft and delicate and, therefore, they lack fossil records. 

(ब्रायोफाइट्स काफी नरम और नाजुक होते हैं और इसलिए, इनके जीवाश्म रिकॉर्ड की कमी होती है।)

> All the views based on the evidence under the following three heads:- 

(निम्नलिखित तीन शीर्षकों के अंतर्गत साक्ष्यों पर आधारित सभी विचार हैं:-)

i. Evidence from comparative morphology of the living plants 

(जीवित पौधों की तुलनात्मक आकारिकी से साक्ष्य)

ii. Evidence from ontogeny of the living plants 

(जीवित पौधों की ओंटोजेनी से साक्ष्य)

iii. Evidence based on analogies with the living plants of other groups 

(अन्य समूहों के जीवित पौधों के साथ समानता पर आधारित साक्ष्य)

> Bryologists are divided into two concepts on the origin of bryophytes. One concept support Algal hypothesis and another one support Pteridophytean hypothesis of the origin of bryophytes.

(ब्रायोफाइट्स की उत्पत्ति पर ब्रायोलॉजिस्ट दो अवधारणाओं में विभाजित हैं। एक अवधारणा शैवालीय परिकल्पना का समर्थन करती है और दूसरी ब्रायोफाइट्स की उत्पत्ति की टेरिडोफाइटियन परिकल्पना का समर्थन करती है।)

1. Algal hypothesis (शैवालीय परिकल्पना):-

> Similarities (समानताएं):-

i. Amphibian nature 

(उभयचर प्रकृति)

ii. Presence of flagellated spermatozoid 

(कशाभ युक्त पुमणुओं की उपस्थिति)

iii. Presence of free water at the time fertilization 

(निषेचन के समय मुक्त जल की उपस्थिति)

iv. Alga like protonema

(शैवाल की तरह प्रोटोनिमा)

> Bower (1908):- Bryophytes show resemblance with green algae (Chlorophyceae)

[ब्रायोफाइट्स हरे शैवाल (क्लोरोफाइसी) से समानता दर्शाते हैं]

i. Photosynthetic pigments like chlorophyll a, Chlorophyll b, Carotene, leutine and violaxanthin 

(प्रकाश संश्लेषक वर्णक जैसे क्लोरोफिल a, क्लोरोफिल b, कैरोटीन, ल्यूटिन और वायोलाग्जैन्थिन)

ii. Starch as reserve food materials 

(संग्रहित खाद्य सामग्री के रूप में स्टार्च)

iii. Filamentous protonema in the juvenile stage  

(तरुण अवस्था में तंतुमय प्रोटोनिमा)

> Fritsch’s view (1916, 1945):- It is based on comparative study of various algal groups:

(यह विभिन्न शैवाल समूहों के तुलनात्मक अध्ययन पर आधारित है:)

i. Gradual reduction of conductive tissue in aerial plants (as in Sargassum) 

[वायवीय पौधों में संवहनी ऊतक की धीरे-धीरे कमी (जैसे कि सारगासम में)]

ii. Heterotrichous habit (as in chaetophorales) 

[विषमतंतुक प्रकृति (कीटोफोरेल्स की तरह)]

iii. Parenchymatous structure of erect filaments ( as in Laminariales and Fucales)

[स्तंभित तंतुओं की मृदूतकीय संरचना (लैमिनेरिएल्स और फ्यूकेल्स में)]

> Smith (1955):-

- Bryophytes have originated from chlorophyceae, primitive form established in area having plenty of water and gradual changes from aquatic to terrestrial, this led to the establishment of more massive plant body and abundance of moisture.

(ब्रायोफाइट्स की उत्पत्ति क्लोरोफाइसी से हुई है, जो प्रचुर मात्रा में जल वाले क्षेत्र में स्थापित आदिम रूप है और धीरे-धीरे जलीय से स्थलीय में परिवर्तन होता है, इससे अधिक विशाल पादप शरीर की स्थापना हुई और नमी की प्रचुरता हुई।)

- As per Smith, Fritschiella; a member of chaetophorales may be probable nearer to the primitive ancestor for bryophytes.

(स्मिथ के अनुसार, फ्रिट्स्चिएला; कीटोफोरेल्स का एक सदस्य संभवतः ब्रायोफाइट्स के आदिम पूर्वज के निकट हो सकता है।)

> Again the supporters of this hypothesis also believed that sex organs of Bryophytes have been evolved from Ectocarpus algae.

(पुनः इस परिकल्पना के समर्थकों का यह भी मानना ​​था कि ब्रायोफाइट्स के लैंगिक अंगों का विकास एक्टोकार्पस शैवाल से हुआ है।)

2. Pteridophytean hypothesis (टेरिडोफाइटियन परिकल्पना):- According to this the bryophytes have been descended from pteridophytes by means of reduction. They formulated their argument on the basis of the following two features: 

(इसके अनुसार ब्रायोफाइट्स कमी द्वारा टेरिडोफाइट्स से उत्पन्न हुए हैं। उन्होंने निम्नलिखित दो विशेषताओं के आधार पर अपना तर्क तैयार दिया:)

i. Close similarity between the sex organs of the two groups. 

(दोनों समूहों के लैंगिक अंगों के बीच घनिष्ठ समानता।)

ii. Resemblance between sporogonium of Anthocerose, Sphagnum and terminal sporangium of fossil pteridophytes – Sporogonites and Horneophyton. 

(स्फेगनम व एन्थोसिरोस के स्पोरोगोनियम की जीवाश्म टेरिडोफाइट्स (स्पोरोगोनाइट्स और हॉर्नियोफाइटन) के शीर्षस्थ बीजाणुधानियों से समानता।)

> This theory is strongly supported by some of the scientists such as Lang(1917), Kidston (1917), Scott(1923), Haskell(1949) and Kashyap (1919). 

[इस सिद्धांत को लैंग (1917), किडस्टन (1917), स्कॉट (1923), हास्केल (1949) और कश्यप (1919) जैसे कुछ वैज्ञानिकों ने पुरजोर समर्थन दिया है।]

> Affinities (समानताएं):-

i. Similarity of their pigments 

(उनके वर्णकों की समानता)

ii. Structure of cell wall 

(कोशिका भित्ति की संरचना)

iii. Food reserves 

(खाद्य सामग्री)

iv. Reproductive methods 

(जनन विधियाँ)

v. Life cycle 

(जीवन चक्र)

> Scott introduce the idea (1911):-

i. Presence of chlorophyll and plastids in the sporogonium of mosses and Anthoceros.

(मॉस और एन्थोसिरोस के स्पोरोगोनियम में क्लोरोफिल और प्लास्टिड की उपस्थिति।)

ii. Presence of stomata on the sporogonium of Anthoceros and the apophysis region of capsule of mosses.

(एन्थोसिरोस के स्पोरोगोनियम और मॉस के कैप्सूल के एपोफाइसिस क्षेत्र पर रंध्रों की उपस्थिति।)

> Kashyap (1919):- Order Equisetales gives 3 orders:-

(गण इक्विसेटेल्स 3 गण देता है:-)

i. Marchantiales (मारकेंशिएल्स)

ii. Jungermanniales (जंगरमेनिएल्स)

iii. Anthocerotales (एंथोसिरोटेल्स)

> Haskell (1949):- He advanced the origin of the bryophytes from the algae through the Psilophytales by simplification.

(उन्होंने सरलीकरण द्वारा साइलोफाइटेल्स के माध्यम से शैवाल से ब्रायोफाइट्स की उत्पत्ति को आगे बढ़ाया।)

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Resemblance of Bryophytes with Algae (Primitive features):-

i. Plant body simple, thalloid and gametophytic.

ii. Autotrophic.

iii. Gametophytic phase is dominant.

iv. Roots are absent.

v. Cell wall is made up of cellulose.

vi. Pigments (chlorophyll a, chlorophyll b, α and β carotene, Lutin, Violaxanthes and Xeoxanthin) are similar in chloroplast.

vii. Vascular tissue is absent.

viii. Antherozoids are motile (bi-flagellated).

ix. Flagella are whiplash type.

x. Water is essential for fertilization.

xi. A filamentous protonema is produced by Bryophytes (juvenile stage in mosses) which resembles with the filamentous green algae.

xii. In order Anthocerotales of Bryophytes, plastids are with pyrenoids which is a characteristic of Chlorophyceae (Green algae).

Resemblance of Bryophytes with Pteridophytes (Advanced features):-

i. Plants are terrestrial.

ii. Primitive simple leafless and rootless sporophytes of Pteridophytes (members of order Psilophytales) can be compared with the sporophytes of Bryophytes.

iii. Sexual reproduction is oogamous.

iv. Androcytes are enclosed by sterile jacket layer.

v. Antherozoids are flagellated.

vi. Water is essential for fertilization.

vii. Permanent retention of zygote within the archegonium.

viii. Zygote forms the embryo.

ix. Moss capsule is similar to terminal sporangium and columella of Psilophytales.

x. Both Bryophytes and Pteridophytes are characterised by heteromorphic alternation, of generation.

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Sporophyte (बीजाणुदभिद):-

> Zygote is the first cell of the sporophyte. 

(जाइगोट बीजाणुदभिद की पहली कोशिका होती है।)

> By repeated segmentation it develops into an elongated embryo. 

(बार-बार विभाजन से यह एक लम्बे भ्रूण के रूप में विकसित होता है।)

> The later by further cell division, cell differentiation and continued growth rapidly grows into an elongated, spindle-shaped structure with a bulbous base, which is known as the sporangium or sporophyte.

(बाद में आगे कोशिका विभाजन, कोशिका विभेदन और निरंतर वृद्धि से यह तेजी से बल्बनुमा आधार युक्त एक लम्बी, धुरी के आकार की संरचना में विकसित हो जाता है, जिसे बीजाणुधानी या बीजाणुदभिद के रूप में जाना जाता है।)

> The sporophyte of Anthoceros is differentiated into two regions: foot and capsule.

(एन्थोसिरोस का बीजाणुदभिद दो क्षेत्रों में विभेदित होता है: फुट और कैप्सूल।)

> Each sporophyte is surrounded at its base by a tubular involucre.

(प्रत्येक बीजाणुधानी अपने आधार पर एक नालनुमा सहपत्र से घिरा होता है।)

a. Foot (फुट):-

- It is a rounded bulbous structure deeply embedded in the tissue of the thallus. 

(यह एक गोलाकार बल्बनुमा संरचना है जो थैलस के ऊतक में गहराई से अंतर्निहित होती है।)

- By means of foot Anthoceros sporophyte is attached is well anchored upon and attached to the thallus. 

(फुट के माध्यम से एंथोसिरोस बीजाणुदभिद अच्छी तरह से थैलस से जुड़ा हुआ होता है।)

- The foot mainly consists of amass of parenchymatous cells.

(फुट में मुख्य रूप से मृदूतक कोशिकाओं का समूह होता है।)

- Seta is absent in Anthoceros sporophyte, instead a zone of meristematic is present, by the activity of which the capsule grows.

(एन्थोसिरोस के बीजाणुदभिद में सीटा अनुपस्थित होता है, इसके स्थान पर एक विभज्योत्तक क्षेत्र मौजूद होता है, जिसकी सक्रियता से कैप्सूल वृद्धि करता है।)

b. Capsule (कैप्सूल):-

- It forms the major and conspicuous part of the sporophyte. 

(यह बीजाणुदभिद का प्रमुख और विशिष्ट भाग बनाता है।)

- It is a long, slender, smooth, upright and cylindrical structure measuring about 2–3 cms in length. 

(यह एक लंबी, पतली, चिकनी, सीधी और बेलनाकार संरचना है जिसकी लंबाई लगभग 2-3 सेमी होती है।)

- Internally, capsule is a complex structure and shows differentiation of tissues. 

(आंतरिक रूप से, कैप्सूल एक जटिल संरचना है और ऊतकों का विभेदन दर्शाती है।)

i. The centre of the capsule is occupied by a sterile mass of tissue known as columella. The columella contains trachied-like cells and is usually 16-celled in cross section. 

(कैप्सूल के केंद्र में कोल्यूमेला नामक ऊतक का एक बंध्य द्रव्यमान होता है। कोल्यूमेला में वाहिनिका-जैसी कोशिकाएँ होती हैं और आमतौर पर अनुप्रस्थ काट में 16-कोशिकाएँ होती हैं।)

ii. Surrounding the columella there is a cylinder of sporogenous tissue which is differentiated into alternative blocks of sterile branched pseudoelaters and spore-tetrads towards the apex. 

(कोल्यूमेला के चारों ओर बीजाणुजनित ऊतक का एक सिलेंडर होता है जो शीर्ष की ओर बंध्या शाखाओं वाले कूटइलेटर्स और बीजाणु-चतुषकों के एकांतरित ब्लॉकों में विभेदित होता है।)

iii. The upper most layer consists of the capsule wall. It is multilayered consisting of 4 – 6 layers of cells. The outer most layer forms the epidermis with distinct stomata. Beneath the epidermis forms the parenchymatous jacket cells with intercellular spaces among them and contains chloroplasts.

(सबसे ऊपरी परत कैप्सूल भित्ति से बनी होती है। यह बहुपरतीय होती है जिसमें कोशिकाओं की 4-6 परतें होती हैं। सबसे बाहरी परत पृथक रंध्रों युक्त अधिचर्म बनाती है। अधिचर्म के नीचे मृदूतकीय जैकेट कोशिकाएं बनती हैं जिनके बीच अंतराकोशिकीय स्थान होते है और इसमें हरितलवक होते हैं।)

> In dry condition, when the capsule looses water, the tip of the capsule gradually shrivels and the capsule dehisces by splitting into two halves exposing spores, thereby shedding off of the spores by hygroscopic movement. 

(शुष्क स्थिति में, जब कैप्सूल जल खो देता है, तो कैप्सूल की नोक धीरे-धीरे सिकुड़ जाती है और कैप्सूल दो हिस्सों में विभाजित होकर बीजाणुओं को सामने कर देता है, जिससे आर्द्रताग्राही गति से बीजाणु बाहर निकल जाते हैं।)

> Dispersal of the spores takes place by air current.

(बीजाणुओं का प्रकीर्णन या फैलाव वायु प्रवाह द्वारा होता है।)

> Spores after liberation from the sporangium undergo a resting period of few weeks or months – then each germinates through germ tube and forms a new Anthoceros thallus.

(बीजाणुधानी से मुक्त होने के बाद बीजाणु कुछ हफ्तों या महीनों की विश्राम अवधि से गुजरते हैं - फिर प्रत्येक बीगाणु अंकुरण नाल के माध्यम से अंकुरित होता है और एक नया एंथोसिरोस थैलस बनाता है।)

Ans.

Identifying Characters:- Notothylas yunnanensis can be easily recognized by:-

 i. The irregularly arranged, subquadrate to subrectangular epidermal cells of the capsule.

ii. The absence of the special dehiscence lines of thick-walled cells along the capsule.

iii. The vermiculate ornamentation of the spores radiating from a central hollow on each proximal surface. > Notothylas yunannensis is closely related to Notothylas depressispora and N. irregularis which also has vermiculate spores with a small depression on each proximal facet. However, they can be distinguished by the shape of the epidermal cells of capsule and the spore ornamentation.

Ans.

Evolution of stele:-

Stele:- The central cylinder or core of vascular tissue, consisting of xylem, phloem, pericycle and sometimes medullary rays and pith, is technically called stele. 

Stelar theory:- 

> Van Tieghem and Douliot (1886) developed this theory. 

> They used the term stele in collective sense and mentioned that the stele is not only made up of xylem and phloem, but the tissue like pericycle, vascular rays and pith are also associated with it. 

> According to them the cortex and the stele are the fundamental parts of a shoot and both these parts are separated from each other by the endodermis. 

> According to stellar theory, primarily there is no fundamental difference in the gross anatomy of stem and roots, because in both of them a stele is surrounded by the cortex is present. 

> Foster and Gifford (1959) have mentioned that the most debated and controversial aspect of “stellar theory is the nature of the anatomical boundaries which separate the cortex from the stele”. 

> According to Van Tieghem and Douliot (1886) the endodermis represents the inner boundary of the cortex. The cells of the endodermal layer have the characteristic casparian strip strips. 

> But in the stems of many seed plants, the characteristic endodermal layer is not present. Some have mentioned that in such cases the pericycle serves as separating layer between the stele and the cortex. 

Types of stele:- 7 types of steles are found in the whole plant kingdom -

1. Protostele

2. Siphonostele

3. Solenostele

4. Dictyostele

5. Polycyclic stele

6. Eustele

7. Atactostele

Note:- Out of these the first 5 types of steles are found only in the stem of pteridophytes. Eusteel is found in the stem of gymnosperms and dicots. Atactostele is found in the stem of monocots.

Note:- The development of stele has also happened in this sequence. Atactosteel is considered to be the most advanced type of stele.

1. Protostele:- This is the most primitive type of stele in which the pith is completely absent and the phloem surrounds the xylem. According to Jeffrey (1898), the protostele is primitive type of stele in vascular plants.

On the basis of the shape of the xylem in the cross section, it is of 4 types -

i. Haplostele:- The xylem appears circular in cross section. It has been observed in fossil genera like Rhynia, Horneophyton and living genera like Selaginella chrysocaulos, S. kraussiana, S. selaginoides, S. willdenowi, Gleichenia dichotoma, Lygodium and Cheiropleuria. 

ii. Actinostele:- The xylem appears star shaped in cross section. Brebner (1902) named such a protostele as actinostele. Eg.- Asteroxylon, Psilotum, Lycopodium serratum and Sphenophyllum. 

iii. Plectostele:- In cross section, the xylem appears as parallel plates. Eg.- Lycopodium clavatum and L. volubile.

iv. Mixed protostele:- In cross section, the xylem is seen scattered in the form of segments. Eg.- Lycopodium cernuum

2. Siphonostele:- In this, pith or pith cavity is found in the center around which vascular tissues are found.

Origin of siphonostele:- There are different views among scientists regarding the origin of siphonostele. But they all agreed that the siphonostele originated from protostele by the formation of a pith in the center. Here, the centrally placed xylem core is replaced with a parenchymatous pith.

Different stages of changing protostele to siphonostele can be observed in the T.S. at different levels in Gleichenia, Osmunda, and Anemia.

There are two views regarding the origin of pith in the siphonostele.

i. Jeffrey’s theory:- 

- According to this theory, the pith is formed as a result of the invasion of cortical parenchymatous cells into the stele. The invasion of the pith occurs through the leaf gap or branch gap.

- Thus pith and cortex are homogeneous structures according to this theory.

- This theory is not accepted by most of the authors since in many pteridophytes there is a stele without leaf gaps but having siphonostele.

ii. Boodle’s theory:- According to the theory proposed by Boodle (1901), and Gwynne Vaughan, the siphonostele has evolved from the protostele by a transformation of the inner vascular tissue into the parenchyma.

On the basis of the location of phloem it is of two types –

i. Ectophloic siphonostele:- Phloem is found around the xylem. Eg.- Osmunda, Schizaea, etc.

ii. Amphiphloic siphonostele:- Phloem is found at both outside and inside the xylem.  Eg. Rhizome of Marsilea, Adiantum, Dipteris.

3. Solenostele:- The vascular tissue in the ectophloic siphonostele forms a leaf gap when it enters the leaf as a leaf trace.

4. Dictyostele:- When the leaves are found densely, many leaf gaps come together causing the vascular tissue of the amphipholic siphonostele to break into many pieces. Each piece is called a meristele and each meristele is a haplostele. In this way many merysteles are found in the form of a circle.

5. Polycyclic stele:- When 2 or more cycles of meristeles are found.

6. Eustele:- When vascular bundles are found in a circle.

7. Atactostele:- When vascular bundles remain scattered throughout the ground tissue.

Ans.

Geobotany (Phytogeography):- The branch of biogeography that is concerned with the geographic distribution of plant species. It is the scientific study of the distribution of plants. Climate is considered the primary control on plant life, but within a particular climatic region the rock beneath soil—known as the parent material of soil—is typically the key factor influencing the vegetation growing above.

Distribution of Bryophytes:-

> Bryophytes are represented by 960 genera and 24,000 species. They are cosmopolitan in distribution and are found growing both in the temperate and tropical regions of the world at an altitude of 4000-8000 feet.

> In India, Bryophytes are quite abundant in both Nilgiri hills and Himalayas; Kullu, Manali, Shimla, Darjeeling, Dalhousie and Garhwal are some of the hilly regions which also have a luxuriant growth of Bryophytes. Eastern Himalayas have the richest in bryophytic flora. A few species of Riccia, Marchantia and Funaria occur in the plains of U.P., M.P. Rajasthan, Gujarat and South India.

> In hills they grow during the summer or rainy season. Winter is the rest period. In the plains the rest period is summer, whereas active growth takes place during the winter and the rainy season. Some Bryophytes have also been recorded from different geological eras e.g., Muscites yallourensis (Coenozoic era), Intia vermicularies, Marchantia spp. (Palaeozoic era) etc.

Ans.

Characteristics of Psilopsida:-

> They are seedless plants.

> They are rootless plants. Rhizomes exist as underground stems where the sporophyte is anchored.

> The shoots grow aerially and branch into smaller stems.

> Rhizomes have hair-like structures called rhizoids which are responsible for the absorption of water and nutrients.

> The vascular system is very simple, primitive and protostelic.

> The plant is usually leafless, and leaves, if present, are in the appearance of scaly appendages or foliage leaves.

> The plant grows as a sporophyte.

> Secondary growth is not present.

Life Cycle of Psilopsida:-

- Sporangia are found on the aerial leaf-like appendages, which bear spores.

- The spores are formed meiotically in groups of four from the spore mother cell.

- The spores are released from the plant and find wet soil to germinate.

- The spores give rise to a gametophyte which is very tiny and colourless.

- The gametophyte bears archegonia and antheridia.

- The fertilisation of the egg and sperm takes place via water.

- The resulting zygote then develops into a new sporophytic body.

Ans.

Spore bearing structure:-

> In Equisetum, spores are formed on aspecialized spore bearing structure known as strobili (singular :

Strobilus), or cone.

> Strobilus, i.e., cone arises singly at the apices of fertile shoots. 

> The primitive type of cone is sub-sessile and is apiculate while the advancedtype is stalked with a rounded apex. 

> In some species, there is a ring likeoutgrowth at the base of the cone, called annulus.

> Each cone or strobilus consists of a thick central axis upon which several densely crowded peltate appendages called sporangiophores  arearranged in whorls. 

> Each sporangiophore (=sporophyll) is a stalked peltatestructure projecting at right angles from the cone axis. 

> Each sporangiophorebears on the underside an elongated sac-like structure called sporangia.

> The number of sporangia per sporangiophore varies from 5-10.

> Mature sporangium is an elongated, cylindrical structure with arounded apex. It consists of a delicate, one cell thick jacket layer. Inside thejacket layer is a mass of sporogenous tissue, from which some of the cells differentiates into spore mother cells and some gets degenerated. 

> The sporemother cells by meiotic division forms haploid spore tetrad.

> Eqiusetum is normally homosporous, and with the formation of spores, gametophytic generation begins. 

Ans.

Life Cycle:-

> The sporophyte reproduces by means of sporangia. 

> As in Marselia, the sporan­gia are aggregated into sporocarps. 

> The details of reproduction have been studied extensively in S. natans. 

> Sporocarp:- 

- The sporocraps appear in clusters ranging in number from 4 to 20. 

- The sporocarps are usually borne on the inner segments of submerged leaves. 

- In arrangement, the sporocarps are sympodial.

- The shape of the sporocarp varies from globose to ovoid, occasionally flattened also with ridged surfaces. 

- The wall of the sporocarp is made up of two layers of cells. The outermost layer when young is clad with hairs.

- Externally all sporocarps are alike. The sporocarps are always bisporangiate. 

- Each sporocarp contain many sori.

- The sporocarp at its base has a stout columnar receptacle which carries the vascular supply into the sporocarp. 

- The receptacle is un-branched in the sporocarps of S. natans.

> Internal structure of sporocarp:-

- A sectional view of mature sporocarp shows a well-developed wall enclosing the, sporangia. 

- Each sprocarp has 4 valves.

> Sporangia:- 

i. Microspoangia:-

- The micro-sporangium consists of a short stalk and a generally ovoid capsule. 

- Enclosed in the sporangium are 16 microspore mother cells and consequently 64 microspores are formed. 

- All the spores attain maturity and survive. 

- The microspores are embedded in the cytoplasmic fluid derived from the tapetum.

- As the spores mature, the tapetal cytoplasm encompassing the spores gets hardened and forms a mass called ‘massula’ or glochidium. 

- The microspores are extremely small, triradiate in appearance and have two wall layers. 

- There is a single nucleus in each microspore.

- Occasionally the number of microspores per microsporangia might vary. In S. auriculata, according to Loyal and Grewal (1966), there are only 8 microspore mother cells and consequently only 32 microspores are formed.

ii. Megasporangia:-

- The mega-sporangium consists of a short stalk and a generally ovoid capsule. 

- The capsule is made up-of a single layer of cells. Internal to the wall of the capsule is a layer of tapetum. 

- Enclosed by the tapetum are found 8 mega-sporocytes which divide meiotically to produce 32 megaspores. Of these spores, all except one degenerate.

> Gametophyte:-

- Two types of gametophytes may be expected since Salvinia is heterosporous. 

- In both micro and mega gametophytes the development is endosporic. 

- The gametophytes begin their development much earlier to the dehiscence of the sporangium.

i. Male gametophyte:- 

- The microsporangium does not dehisce, hence the microspores develop within the microsporangium. 

- At the first sign of development, the microspore gets divided into three cells. Of these, the lowest divides slightly obliquely to form a prothallial cell. 

- Further divisions are restricted only to the upper two cells. 

- From these two cells, by successive divisions, two spermatogenous cells and four sterile cells are formed.

- The four sterile cells constitute the jacket cells. 

- The two spermatogenous cells by further divisions, form eight spermatocytes which appear in two clusters separated by means of a sterile cell. 

- When the gametophytes are mature the sterile cells (Jacket cells) disintegrate, releasing the multi-flagellate spermatozoids which develop from the spermatocytes.

ii. Female gametophyte:-

- The megaspore generally floats on the surface of water in a prone position. 

- Prior to the first division, the nucleus migrates to the apical portion of megaspore. 

- First division of the nucleus results in forming two unequal cells. 

- The upper cell is small and lenticular while the lower cell is very large and is filled with plenty of nutrition.

- Most of the gametophyte is derived from the upper lenticular cell, while in the lower large cell there are only free nuclear divisions. 

- This multinucleate cell functions as a store house of reserve food material. 

- The upper lenticular cell by means of several divisions forms a lobed apical cushion which comes out penetrating the spore wall and perispore.

- Archegonia appear on this apical cushion. 

- Generally, two to four archegonia develop in the apical cushion. 

- The archegonia are deeply sunk in the apical cushion. They have a very short neck, an egg cell, a venter canal cell and a two nucleate neck canal cell.

> Fertilization:- 

- The female gametophyte at maturity exposes the archegonia. 

- In the archegonium, the neck canal cell and venter canal cell disorganize to facilitate the entry of the sperms. 

- A large number of sperms enter into the neck of the archegonium while only one succeeds in fusing with the egg. 

- The resultant zygote develops into embryo.

> Embryogeny:-

- The first division of the zygote is longitudinal i.e., parallel to the long axis of the neck of the archegonium the next division is transverse resulting in the formation of a quadrant. 

- Vertical division of the quadrant cell results in the octant stage.

- The basal cells of the octant form a foot which is haustorical in nature. 

- Of the remaining upper four cells of the octant, the two anterior ones-develop into the first leaves. 

- Of the remaining two cells, one gives rise to the stem apex while the other is functionless.

- There are no roots in Salvinia. 

- Further divisions from the octant stage onwards are bit difficult to follow. 

- From the octant cells, a cell plate is formed, which functioning like a column connects the foot with the leaf and stem apex. 

- According to some workers the foot plus the column represents a vestigial root. 

- The leaf segment enlarges and grows into a cordate leaf. 

- The stem apex divides actively and forms the rhizome.

Ans.

Soral evolution:-

Sorus:- It is brownish or yellowish cluster of spore-producing structures (sporangia) usually located on the lower surface of fern leaves. A sorus may be protected during development by a scale or flap of tissue called an indusium.

Types of sorus:-

i. Simple sorus:-

> The Simplices are primitive and extend to the Paleozoic. 

> All sporangia within a sorus may be at the same stage of development (Simplices).

> The sporangia in such a sorus development simultaneously and all of them mature together. 

> Eg.- Ophioglossum and Osmunda.

ii. Gradate sorus:-

> In such cases the internal space within the radial sorus gets filled by overlapping sporangia. 

> Overcrowding results and there is no space for the proper dehiscence of sporangia and consequently some of them do not dehisce. 

> The Gradate with an oblique annulus, occupy a middle position and have been discovered in the Mesozoic. 

> Eg.- Dicksonia, Loxosoma, Trichomanes, Cyathea, Alsophila etc.

iii. Mixed sorus:-

> The spores are released in a staggered fashion and even if the environmental conditions are not favorable when the spores are initially released; this problem is solved by a constant crop of spores over a given length of time. 

> Mixtae annulus is present but in a vertical fashion. 

> Eg.- Polypodiaceae (Adiantum, Pteris, Pteridium, Davallia) Polypodiaceae

Indusial protection:- The indusium may be formed as an epidermal outgrowth covering receptacle and sporangia (true indusium) or it may merely be the in turning of the margin of the leaf to protect the sporangia (pseudo indusium or false indusium).

Position of sorus in ferns:- The Ophioglossales are group of interesting ferns in which the sporangia are marginal in position. 

> In Maeattia, Angiopteris, Danaea etc. the sori are elongagated and are situated below the lateral veins. 

> In christensia the sori are naked, circular and are irregular arranged between the lateral veins. 

> In Adiantum the sporangia develop on the underside of special marginal flaps of lamina that become reflexed and protect the sorus 

> The sori in Mattoniaceae are ventral in position and are usually arranged in two rows on either side of the midrib. 

> In Glecheniaceae, the sporangia from distinct sori on the ventral surface of the leaves. 

> The sporangia in Osmunda, Davalia, Trivhomanes and many other ferns are also marginal in position.

> In Marsileales and the Salviniales the sporangia develop in sori that are borne within distinct structure called the Sporocarp.

- In Salviniales the smaller sporocarp contain many microsporangia each and the larger ones contain one or more megasporangia per sporocarp. 

- The sporocarp in Marsilea enclose sori that contain both micro and megasporongia. 

Ans.

Classification of Bryophytes (ब्रायोफाइट्स का वर्गीकरण):- According to the newest classification, Bryophyta is split into three classes:

(नवीनतम वर्गीकरण के अनुसार, ब्रायोफाइटा को तीन वर्गों में विभाजित किया गया है:)

1. Hepaticopsida (Liverworts) 

2 Anthocerotopsida (Hornworts)

3. Bryopsida (Mosses)

1. Hepaticopsida (Liverworts):- 

> The name hepaticopsida comes from the word “hepatic” which means liver. 

(हिपेटिकोप्सिडा नाम "हिपेटिक" शब्द से आया है जिसका अर्थ है यकृत।)

> The most basic bryophytes are liverworts. 

(सबसे आधारभूत ब्रायोफाइट्स लिवरवॉर्ट्स हैं।)

> They prefer moist rocks and wet soil to live in. 

(वे रहने के लिए नम चट्टानें और गीली मिट्टी पसंद करते हैं।)

> Because they dwell near water, their chances of drying are much reduced. 

(क्योंकि वे जल के पास रहते हैं, उनके सूखने की संभावना बहुत कम हो जाती है।)

> The gametophyte plant is either thalloid or foliose.

(युग्मकोदभिद पौधा या तो थैलॉइड या पत्तेदार होता है।)

> Thalloid forms are dorsiventral, lobed, and dichotomously branched.

(थैलॉइड रूप पृष्ठाधरी, पालित और द्विभाजित शाखा वाले होते हैं।)

> Rhizoids are unicellular, unbranched and of 2 type:

(मूलाभास एककोशिकीय, अशाखित और 2 प्रकार के होते हैं:)

> Sex organs are borne dorsally embedded in gametophytic tissues.

(लैंगिक अंग युग्मकोदभिद ऊतकों में पृष्ठीय रूप से धँसे होते हैं।)

> The sporophyte is a compilation of only capsule (in Riccia) or foot, seta, and capsule (in Marchantia).

The columella is absent in the capsule.

(बीजाणुदभिद केवल कैप्सूल (रिक्सिया में) या फुट, सीटा और कैप्सूल (मार्केन्शिया में) का संकलन है। कैप्सूल में कोल्यूमेला अनुपस्थित होता है।)

> Sporogenous tissues develop from endothecium.

(बीजाणुजनित ऊतक एन्डोथेसियम से विकसित होते हैं।)

> Hepaticopsida is further divided into 5 orders:

(हेपेटिकॉप्सिडा को आगे 5 गणों में विभाजित किया गया है:)

a. Sphaerocarpales:- 2 families: (2 कुल)

i. Sphaerocarpaceae:- Eg.- Sphaerocarpos, Geothallus

ii. Riellaceae:- Eg.- Riella

b. Marchantiales:- 4 families: (4 कुल)

i. Ricciaceae:- Eg.- Riccia, Ricciocarpus, Tesselina (Oxymitra)

ii. Targionaceae:- Eg.- Targionia, Cyathodium, Aitchisoniella

iii. Monocleaceae:- Eg.- Monoclea

iv. Marchantiaceae:- Eg.- Marchantia, Plagiochasma, Dumortiera, Lunularia, Reboulia, Grimaldia, Monoselenium

c. Jungermanniales:- 3 families: (3 कुल)

i. Ricardiaceae (Aneuraceae):- Eg.- Ricardia (Aneura)

ii. Blyttiaceae (Pallavaciniaceae):- Eg.- Blyttia

iii. Codoniaceae:- Eg.- Pellia, Petalophyllum, Fossombronia

d. Calobryales:- 1 family: (1 कुल)

i. Calobryaceae:- Eg.- Calobryum, Haplomitrium

e. Takakiales:- 1 family: (1 कुल)

i. Takakiaceae:- Eg.- Takakia

2. Anthocerotopsida (Hornworts):-

> They are commonly known as hornworts.

(इन्हें आमतौर पर हॉर्नवॉर्ट्स के नाम से जाना जाता है।) 

> The gametophytic body is flat, dorsiventral, simple thalloid, and has no internal differentiation.

(युग्मकोदभिद शरीर चपटा, पृष्ठीय, सरल थैलॉइड होता है और इसमें कोई आंतरिक विभेदन नहीं होता है।)

> Rhizoids are unicellular, unbranched and smooth-walled.

(मूलाभास एककोशिकीय, अशाखित और चिकनी भित्ति वाले होते हैं।)

> Each cell has one chloroplast with a pyrenoid.

(प्रत्येक कोशिका में पाइरेनॉइड के साथ एक क्लोरोप्लास्ट होता है।)

> Sex organs are present dorsally embedded in the thallus.

(लैंगिक अंग थैलस में पृष्ठीय रूप से धँसे होते हैं।)

> Sporogenous tissues develop from amphithecium.

(बीजाणुजनित ऊतक एम्फ़िथेशियम से विकसित होते हैं।)

> Pseudoelaters are present in the capsule.

(कैप्सूल में कूटइलेटर्स पाये जाते हैं।)

> The columella is present within the capsule, which originates from the endothecium.

(कोल्यूमेला कैप्सूल के भीतर मौजूद होता है, जो एंडोथेसियम से उत्पन्न होता है।)

> It has only one order:

(इसका केवल एक ही गण है:)

a. Anthocerotales:- 2 families: (2 कुल)

i. Anthocerotaceae:- Eg.- Anthoceros, Paeoceros, Dendroceros, Megaceros

ii. Notothylaceae:- Eg.- Notothylas

3. Bryopsida (Mosses):-

> They are commonly called mosses.  

(इन्हें आम तौर पर मौस कहा जाता है।)

> The gametophyte is divided into protonema and foliose gametophore.

(युग्मकोदभिद को प्रोटोनिमा और पर्णीय गैमेटोफोर में विभाजित किया गया है।)

> Foliose gametophore is formed of the stem as an axis and leaves without a midrib.

(पर्णीय गैमेटोफोर एक अक्ष के रूप में तने और मध्यशिरा रहित पत्तियों से बना होता है।)

> Rhizoids are multicellular with oblique septate.

(मूलाभास तिरछे पट्ट युक्त बहुकोशिकीय होते हैं।)

> Sex organs are borne apically on the stem.

(लैंगिक अंग शीर्षस्थ रूप से तने पर उत्पन्न होते हैं।)

> Elaters are absent.

(इलेटर अनुपस्थित होते हैं।)

> The sporophyte is differentiated into foot, seta and capsule.

(बीजाणुदभिद को फुट, सीटा और कैप्सूल में विभेदित किया जाता है।)

> Sporogenous tissues develop from endothecium.

(बीजाणुजनित ऊतक एन्डोथेसियम से विकसित होता है।)

> The columella is present.

(कोल्यूमेला उपस्थित होता है।)

> Separation of the lid is the result of the Dehiscence of the capsule.

(ढक्कन का अलग होना कैप्सूल के फूटने का परिणाम है।)

> Bryopsida is further divided into 3 sub-classes:

(ब्रायोप्सिडा को आगे 3 उप-वर्गों में विभाजित किया गया है:)

a. Sphagnidae:- 1 order: (1 गण)

I. Sphagnales:- 1 family: (1 कुल)

i. Sphagnaceae:- Eg.- Sphagnum

b. Andreidae:- 1 order: (1 गण)

I. Andreales:- 1 family (1 कुल)

i. Andreaceae:- Eg.- Andrea (Granite moss)

c. Eubryidae (Bryidae):- 3 orders: (3 गण)

I. Polytrichales:- 1 family: (1 कुल)

i. Polytrichaceae:- Eg.- Polytrichum, Pogonatum, Atrichium, Oligotrichum, Lyellia

II. Funariales:- 5 families (5 कुल)

i. Gigaspermaceae

ii. Funariaceae:- Eg.- Funaria

iii. Disceliaceae

iv. Oedipodiaceae

v. Splachaceae

III. Buxbaumiales:- 1 family:

i. Buxbaumiaceae:- Eg.- Buxbaumia, Diphyscium

Ans.

Life Cycle:-

> Dioecious plant body.

> Male plant is represented by a single mussel shell shaped male bract which contains a single globular antheridium.

> Female plant is relatively large than the male plant and represented by 2 or 4 rows of very small lanceolate leaves which are without midrib. Leaves are only present in B. himalayensis but absent in B. aphylla. A single archegonium present at the apex of the female shoot.

> Some authors wrote that sex organs are produce on protonema like structures.

5. Study of sporophyte:-

> Structure of sporogonium is similar to Polytrichum.

> Beak absent and operculum is dome shaped.

> 64 peristome teeth in three rings:

i. Exostome (Orthodontous)

ii. Mesosome (Membranous)

iii. Endostome (Nematodontous)

Ans.

Heterospory:- The phenomenon of the development of two types of spores (differing in size, structure and function) by the same species is known as heterospory.

> The two different sizes are smaller spores also known as microspores and the larger spores  also known as megaspores.

> Rashid (1999) listed nine genera as living examples of heterosporous pteridophytes. e.g. Selaginella, Isoetes, Stylites, Marsilea, Pilularia, Regnellidium, Salvinia, Azolla and Platyzoma.

Origin of Heterospory:- The origin of heterospory can be better discussed on the basis of evidences from paleobotany, developmental and experimental studies.

1. Palaeobotanical evidences:- 

- It has been suggested that heterospory arose due to degeneration of some spores in a few sporangia. As more nutrition becomes available to less number of spores, the surviving spore grow better, hence increase in their size.

- Palaeobotanical evidences show that the earlier vascular plants were all homosporous and the heterosporous condition appeared subsequently in the lowermost upper Devonian.

- A number of heterosporous genera belonging to the Lycopsida, Sphenopsida and Pteropsida were known in the late Devonian and early Carboniferous periods.

2. Evidences from Experimental Studies:-

- Experimental studies on Selaginella (Goebel, 1905) and Marsilea (Shattuck, 1910) suggest that nutritional factors mainly govern the heterospory.

- Under conditions of low light intensity, the photosynthetic activity of Selaginella was retarted and it produced microsporangia.

- By sudden lowering of the temperature, the size of the microspores in the sporocarp of Marsilea increases by six times.

3. Evidences from Developmental Studies:-

- In heterosporous pteridophytes, the development of micro and megasporangia follow the same pattern. While in megasporangia most of the spore mother cells degenerate but in microsporangia only a few mother cells are disorganized.

- The phenomenon of heterospory becomes distinct either before or after meiosis in Selaginella. Isoetes, it is distinct before meiosis.

Importance of heterospory:-

i. The differentiation in the size of the spore is directly related to the differentiation of sex of the gametophyte. Therefore, heterospory is an expression of sex determination in plants.

ii. Because of heterospory, plants become free to grow in varied environmental conditions, instead of only aquatic surroundings.

iii. It ultimately leads to seed development.

iv. The megaspore having female gametophyte derives nourishment from sporophyte and thus remains independent from external factors.

Seed habit:- Because of heterospory, the gametophytic tissue is reduced. Partial or complete retention of megasporangium and female gametophyte on the sporophyte also takes place. They show reduction in megaspores and male gamete. All these characters show a tendency towards seed habit.

Origin of seed habit:- One of the most important advantages of heterospory is the formation of seed habitat. The origin of seed habit is associated with the following:

i. Production of two types of spores (heterospory).

ii. Reduction in the number of megaspores finally to one per megasporangium.

iii. Retention and germination of the megaspores and fertilization of the egg.

iv. Continued development of the fertilized egg into the embryo while still in situ.

Seed habit in Selaginella:- Selaginella exhibits remarkable approach to the seed habit because of the following features:

i. The heterospory occurs in almost all the species of Selaginella.

ii. In most species only one functional megaspore mother cell is produced which by reduction division produces four haploid megaspores. In some species e.g. rupestris and S. monospora only one megaspore is formed in each megasporangium.

iii. Germination of megaspore starts within the megasporangium, but its stage and time of retention within megasporangium differ in different species.

iv. Fertilization and embryo development also takes place within the megasporangium.

Although certain species of Selaginella suggest early stages in the evolution of seed habit, Selaginella should not be considered as an ancestor to seed plants because:

i. Absence of integuments around the megasporangia.

ii. Absence of permanent retention of megaspores within megaspoarangia except a few species.

iii. Absence of complete histological fusion between megasporangium wall and megaspore.

iv. After the development of embryo there is lack of resting period.

Therefore, Selaginella has considerably advanced towards seed habit but it’s approach to true seed is not complete.

Ans.

Isoetes:-

1. Systematics:-

Division:- Lycophyta

Class:- Ligulopsida

Order:- Isoetales

Family:- Isoetaceae 

Genus:- Isoetes 

2. Habit and Habitat:-

> Isoetes includes 60 to 70 species and is world wide in distribution. Nearly 10 species are reported

from India, such as:-

i. Isoetes coromandelina:- Reported from Kerala, Tamil nadu, Andhra Pradesh Maharashtra and Gujrat Padampur and Bengal Madhya Pradesh, Uttar Pradesh, Bihar and Orissa.

ii. Isoetes coromandelina Sub Sps. branchyglossa:- West Bengal.

iii. Isoetes bilaspurensis:- Madhya Pradesh.

iv. Isoetes dixitii:- Maharashtra.

v. Isoetes indica:- Uttar Pradesh, Madhya Pradesh and Tamilnadu.

vi. Isoetes panchananii:- Madhya Pradesh and Maharashtra.

vii. Isoletes pantii:- Madhya Pradesh.

viii. Isoetes sahyadriensis:- Maharashtra and Tamil nadu.

ix. Isoetes Sampath Kumarnii:- Maharashtra and Tamil nadu.

x. Isoetes unilocularis

3. Study of sporophyte:-

> Sporophyte plant body are small ranging from 5 cm to 60 cm. in length, herbaceous and perennial. 

> It consist of short, fleshy, upright corm-like axis - which is very specialized. 

> On the upper surface of the axis are born densly-crowded cluster of quill-like leaves, hence called quillwort. 

> On the basal part of the axis there are two or three deep vertical grooves that makes it two or three lobed. (In Isoetes coromandelina is four or five-lobed). 

> The roots are borne on the side of the grooves. 

> The upper leaf bearing parts is known as stem and lower parts contain roots, which is designated as rhizomorph. 

> The vertical growth is very slow. 

> In width it range from 0.5 to 2.5 cm. but in some forms it may reach upto 4 cm or more.

> Roots in Isoetes arise from the lower portion of the fleshy axis and are unbranched rarely branched dichotomously.

> Leaves are borne on the upper surface of the axis. 

> Each leaf has a thickened and expanded colourless base and a tapering distal portion which is owl shaped and pointed. 

> The leaves are 30 to 70 cm long and are arranged in a dense spiral with phyllotaxy of 3/8, 5/13 and 8/21. 

> A persistent more or less triangular ligule are found on the concavity. 

> The leaf has a median unbranched vein.

> Apical growth is initiated by a group of apical cells. 

> Internal structure of corm:- 

- Longitudinal section of the Corm in two planes gives detailed idea of anatomical feature.

i. In a plane at right angles to the basal groove and through each lobe.

ii. In the plane along the externally seen basal groove.

- In the centre of the corm is stele. Stele is protostele with superparenchymatized layer of pith. 

- The secondary growth is by cambium which is composed of two parts:

i. A lateral meristem which surrounds the upper portion of the vascular cylinder and encloses the sides of the lower root bearing portion of the corm.

ii. A basal meristem which is continuous with the lateral meristem arranged to form a ribbon.

> Internal structure of Leaf:- 

- Cross section reveals semicircular or more or less rhombic. 

- Mesophyll cells undifferentiated. 

- The stomata are situated over the air cavities. 

- The vascular bundle is small and collateral.

- The ligule remain situated on the adaxial side of the leaf base consist of only of Parenchyma. 

- Its base thickens and penetrate or little into the leaf as glossopodium. 

4. Reproduction:-

> Every leaf in both genera is potentially a sporophyll because each bears sporangium, normal or abortive. 

> The sporophyte are heterosporous. 

> The development of sporangium is of eusporangiate type. 

> The mature sporangia are of two kinds: microsporangia and megasporangia but they are much alike in size and appearance. 

> The microsporangia bear numerous (1,50,000 to 2,50,000) small Microspore. 

> Megasporangia bear 50 to 500 large megaspore. 

> Spore germinates as soon as they are shed from the microsporangium.

> The mature microgametophyte is wholly endoscopic and consists of a small prothallial cell and one antheridium. 

> Antherozoids are biflagellated. 

> The ninecelled microgametophyte is more reduced than in any other pteridophyte.

> The megaspore consist of considerable amount of reserve food material and large nucleus. 

> The archegonia are developed from the superficial cell. 

> At maturnity, the neck canal cell and ventral canal cell disintegrate and the female gametophyte is initially endospore. 

> No suspensor is formed and the embryogeny is exoscopic.

5. Phylogeny:- 

> Phylogeny:- The history of the evolution of a species or group, especially in reference to lines of descent and relationships among broad groups of organisms.

> Fossilised specimens of I. beestonii have been found in rocks dating to the latest Permian.

> Quillworts are considered to be the closest extant relatives of the fossil tree Lepidodendron, with which they share some unusual features including the development of both wood and bark, a modified shoot system acting as roots, bipolar growth, and an upright stance.

> Studies indicates that the Isoetes crown group which exist today evolved from a single lineage in the early Cenozoic.

Ans.

Study of sporophyte:-

> In most of the species of Ophioglossum and Botrychium the sporophyte has a short, erect, subterranean rhizome. In O. pendulum and, intermedium the rhizome is markedly dorsiventral.

> The lamina of the leaf in most species except in few species as e.g. O. palmatum is simple, entire and narrowly linear to broadly oval in outline.

> In O. palmatum the mature leaves are more or less clearly dichotomous and the lamina is palmately divided into a number of norrow lobes.

> In O. pendulum the long, pendent leaf may reach a length of 1.5 mm or more.

> The roots may be unbranched in sub genus Euophioglossum or branch freely in subgenus ophionderma or branch freely in subgenus churoglossa. 

> The roots are mycorrhizic.

Reproduction:-

> The sporangia are born on fertile spike that arise on the basal portion of the sterile leaf.

> After maturity the sporangium delisces by a transverse cleft in Ophioglossum.

> L.S. spike or cone:- All sporangia are at the same stage of development.

> Prothalus:- Spore germinates to give rise subterrenian prothallus.

> Embryo is always exoscopic.