Riccia
• 1. Riccia – Structure and Reproduction
• Systematic position :Riccia belongs to the family Ricciaceae, order Marchantiales, class Hepaticopsida and division Bryophyta.The common Indian species are Riccia siliata, R. hitra, R. discolor, R. glauca, R. gangetica, R.melansspora, R. hirta, R. crystallina. Habitat or occurrence: The genus Riccia with about 200 species, is cosmopolitan in its distribution and commonly grows in moist soils especially during and after rains. Majority of the species are terrestrial, a few are free-floating or submerged aquatics e. g. R. fluitans, R.natans. The plant R. crystallina occurs at an altitude of 14,000 ft. in Western Himalayas. External morphology In Riccia the gametophytic plant body is the dominant phase in the life cycle. • The gametophyte is a prostrate, dorsiventrally flat, dichotomously branched, green, fleshy thallus. • Each branch is either liner or wedge-shaped or obcordate and as the dichotomous branches begin to grow together from one place, the plant usually exhibits a shape of a rosette or a circular patch. • Each branch is thick in the median region and thin towards the margin. Each branch shows a conspicuous, longitudinal furrow along the mid-dorsal line ending in a notch at the tip where the growing point is located. • On the ventral surface are present two types of outgrowths, the multicellular scales and the unicellular rhizoids. The scales are multicellular, pink, red, violet or black and one-celled thick structures arranged in a transverse row. The scales are more crowded near the apex and overlap the growing point. In the mature portion, each scale splits up into two so that there seem to be two rows of scales along the two margins of the thallus. Scales mainly protect, the growing point and increase absorptive surface. • The rhizoids are unicellular, elongated, tubular hair like structures which attach the thallus to the substratum and absorb water and nutrient solution. They are analogous to the roots
• Systematic position :Riccia belongs to the family Ricciaceae, order Marchantiales, class Hepaticopsida and division Bryophyta.The common Indian species are Riccia siliata, R. hitra, R. discolor, R. glauca, R. gangetica, R.melansspora, R. hirta, R. crystallina. Habitat or occurrence: The genus Riccia with about 200 species, is cosmopolitan in its distribution and commonly grows in moist soils especially during and after rains. Majority of the species are terrestrial, a few are free-floating or submerged aquatics e. g. R. fluitans, R.natans. The plant R. crystallina occurs at an altitude of 14,000 ft. in Western Himalayas. External morphology In Riccia the gametophytic plant body is the dominant phase in the life cycle. • The gametophyte is a prostrate, dorsiventrally flat, dichotomously branched, green, fleshy thallus. • Each branch is either liner or wedge-shaped or obcordate and as the dichotomous branches begin to grow together from one place, the plant usually exhibits a shape of a rosette or a circular patch. • Each branch is thick in the median region and thin towards the margin. Each branch shows a conspicuous, longitudinal furrow along the mid-dorsal line ending in a notch at the tip where the growing point is located. • On the ventral surface are present two types of outgrowths, the multicellular scales and the unicellular rhizoids. The scales are multicellular, pink, red, violet or black and one-celled thick structures arranged in a transverse row. The scales are more crowded near the apex and overlap the growing point. In the mature portion, each scale splits up into two so that there seem to be two rows of scales along the two margins of the thallus. Scales mainly protect, the growing point and increase absorptive surface. • The rhizoids are unicellular, elongated, tubular hair like structures which attach the thallus to the substratum and absorb water and nutrient solution. They are analogous to the roots