Q.8. Differentiate between the structure of Riccia and Marchantia thallus. (2010, 12)
Ans.
Q.9. Describe the salient features of Riccia and Marchantia. (2013)
Related Questions -
Q. Describe the identifying characters of Pellia, Anthoceros and Funaria. (2007, 10)
Q. Differentiat between the structure of Riccia and Marchantia thallus. (2005)
Q. Give an illustrated account of gametophytic structure of Riccia, Pellia and Anthoceros. (2004)
Q. Give identifying characters of Riccia, Marchantia, Pellia and Anthoceros thallus growing in nature. (1996, 98)
Ans. Characters of Riccia: -
1. The gametophyte plant body is a thallus, which is prostrate, flat, dorsiventral, ribbon-like and usually some what fleshy.
2. Its branches dichotomously.
3. Each branch of the thallus is usually linear to wedge shaped or abeardate.
4. In terrestrial forms, the plants take a typical rosette farm due to the presence of several dichotomies close to each other.
5. The thallus of R. reticulata are relatively thick sulcale and overlapped. R melanospora is characterised by the presence of several hairy epidermal outgrowths on the dorsal surface of the thalli.
6. In most of the species each branch of the thallus has a mid-rib on the dorsal surface. It is a shallow groove and known as dorsal groove or furrow.
7. At the apical portion of the thallus the mid rib ends in a depression known as apical notch.
8. The ventral surface of the thallus bears many rhizoids and scales. They are of two types
(i) Smooth walled rhizoids (ii) tuberculate rhizoids.
9. R.melanospara and R.robusta have mostly smooth walled rhizoids.
10. The rhizoids attached to the substratum and they also help in absorpiton of water and nutrients from the soil.
11. The scales are multicellular, their pink or violet colour is due to the presence of anthocyanin pigments.
12. Plants growing in moist terrestrial habitats usually have small and ephemeral scales, where as dry habitats have large and persistent scales.
Characters of Marchantia: -
1. The gametophyte of Marthantia is prostrate, dorsiventral and dichotomously branched like that of Riccia.
2. Each branch of the thalli has a distinct midrib which is marked on the dorsal surface by a shallow groove.
3. The apex of each branch is notched and a growing point is situated at the base of each notch.
4. The mature thallus may be 2-10 cm. in length.
5. A close observation of the dorsal surface disclose many polygonal or rhomboidal areas which indicate the outline of the underlying air chambers of the thallus just beneath the upper epidermal layer.
6. The polygonal area has an airpore in its entrance.
7. The dorsal surface of the thallus bears gemma cup along the midrib they are cup-shaped structure with filled margins.
8. The gemma cup help in vegetative reproduction.
9. The branch of the thallus grows by a growing point which is situated at the apex of the thallus in a groove called apical notch.
10. The ventral surface of the thallus bears rhizoids and scales on both sides of the midrib. The rhizoids are colourless and unicellular.
11. The scales are multicellular, violet in colour due to the presence of anthocynin pigments in their cytoplasm. In M. polymorpha there are three or four rows of scales on either side of the mid rib.
12. The sexually mature thalli possess specialized erect branches,the gametophores which bear sex organs. The branches present on the male thalli with antheridia and are known as antheridiophores.
13. Female thalli bear archegonia and are called archegoniophores.
Characters of Pellia: -
1. The mature gametophyte of Pellia is simple, prostrate, dorsiventrally flattened, usually thin and dichotomously branched.
2. On the dorsal surface there is a median broad indistinct midrib.
3. The thallus is irregularly lobed with sinuous margin. The lobes are also dichotomously branched just like thallus.
4. On the ventral surface numerous unicellular smooth walled rhizoids are borne in the region of the midrib but the tuberculate rhizoids and ventral scales are absent.
5. The growing point of thallus is situated in the apical notch.
6. On damp ground the thallus is broader, robust and elongated, on dry sandy soil the thallus is short stunted, thicker and stouter with an indistinct midrib.
7. The antheridia are borne on the dorsal surface of the thallus along the midrib it is numerous wost like projections scattered over the upper surface of midrib.
8. The archegonia are formed in groups of four to twelve at the anterior end of a branch just behind the growing point is projected by an involucre which is cylindrical in P.neesiana.
Characters of Anthoceros: -
1. The gametophyte plant body is a small, dark green, thin dorsiventral and prostrate thallus.
2. It is subarbiculate and lobed. It is long and pinnately divided in A. hallii and bilobed in A. himalayansis.
3. The thallus is thick in the middle but it has in distinct midrib.
4. The dorsal surface of the thallus is smooth (A. laevis) velvety (A. crispulus) or rough(A. fusiformis).
5. The ventral surface bears many unicellular, unbranched, smooth walled rhizoids along the median line.
6. Juberculate rhizoids and scales are absent.
7. The mature thalli have erect elongated and cylindrical porophytes which usually develop during September-October.
8. Anthoceros may be monoecious (homothallic) or dioecious (heterothallic).
9. Both types of sex organs are initiated just behind the growing point. The antheridia and archegonia are embedded in the dorsal region of the thallus.
Characters of Gametophyte of Funaria: -
1. The gametophyte of Funaria is found in two forms:
(i) Protonema - It is filamentous, chlorophyllose and branched which consists-of buds.
(ii) Gametophore - Main axis bears small leaves and rhizoids.
2. Gametophytic plant body consists of a main axis on which leaves are arranged spirally.
3. Branches are monopodeal, Letral, below the leaf.
4. Leaves are green small, oval, sesslie and simple.
5. Many rhizoids are attached to the basal portion of stem. These are multicellular, colourless and branched.
6. Reproductive organs are situated at the apex of plant.
7. The plant of Furania is monoecious or dioecious.
8. Male and female reproductive organs are found on separate branches. Male at the apex of antheridial branch and feamle on the tip of archegonial branch.