COMMENTS ON RICCIA
Habit
Riccia is a common terrestrial genus except an aquatic B.fluitani which is found in free floating condition. It grows in moist places like, rocks, tree trunks, walls, banks of rivers and streams.
i) Dorsal surface:
The dorsal surface is porous and exhibits a thick conspicuous mid. rib groove extending from base upto apex. A depression at the apical portion of each branch forms a notch, the growing point.
ii) Ventral Surface:
The margin of the ventral surface of thallus is furnished with the rows of violet-colored scales which are crowded by the notch but loosely arranged away from the notch. They are multicellular thin and have a celled layer without appendages.
iii) Rhizoids:
The ventral surface possesses many thin elongated unicellular threads like rhizoids, at the central line. They are of two types long, simple smooth walled rhizoid and tuberculated rhizoid with inner wall projecting into peg-shaped structures.
Internal Structure of Thallus
i) Storage Region:
The thallus is internally differentiated into the upper dorsal and lower ventral region. The ventral region or storage region is composed of compactly packed parenchymatous cells enclosing starch grains the rhizoids emerge from its lower epidermis.
ii) Photosynthetic Region:
The dorsal region or photosynthetic region consists of many vertical rows of chlorophyllous cells originating from the upper layer of the ventral region. They are separated by narrow ventral air canals, which open through non-organized air pores of the dorsal surface.
iii) Antheridium:
It is a club-shaped structure standing on a few celled stalks. It consists of a single layer/jacket wall enclosing a number of audrocite mother cells, and antherozoids. The antherozoid is long, Coiled, uninucleate and biciliate.
iv) Archegonium:
It is a flask shaped structure with a long neck and a swollen venter. It is attached to the thallus by a short stalk. The neck has 6-9 neck calls arranged in six vertical rows surrounding the neck canal. The neck canal is covered by four large cover cells at the top. The ventral consists of an upper ventral canal cell and lower single large egg.
v) Sporangium:
It is a spherical body called capsule or spore sac. It consists of many spore tetrads surrounded by a single layered capsular wall. It is externally invested by two layered calyptra, an extension of ventral tissue. The spore tetrads Containing four spores are arranged tetrahedrally. The spores may remain attached to one another within a common spherical sheath.
