(i) Thallus: Riccia is a gametophyte plant. Its body cannot be divided into roots, stems and leaves. That is, they are thallus shaped. Thallus green, obtuse, succulent, recumbent, opposite and flattened. It is bifurcated. Each branch has a large groove at the tip. It is called apical notch. The surface of the thallus has a longitudinal groove. This is called dorsal groove. A median vein runs longitudinally along the dorsal groove. Many thallus arranged together like rose petals. This condition is called rosette. The thallus bears gemma cups which reproduce by organogenesis. Being green, it can produce food through the process of photosynthesis.
(ii) Rhizoids: Slender, filamentous, unbranched, colorless unicellular rhizoids arise from the lower part of Riccia-thallus. It is of two types. Smooth and rough rhizoids. The irregular rhizoids have nail-like nodules. Rhizoids anchor the thallus to soil or other material and absorb water and mineral salts. Aquatic species of Riccia do not have rhizoids.
(iii) Scales: Thin, filiform, unbranched, colorless and multicellular scales arise from the lower part of Riccia thallus. It attaches the thallus to the soil or other material and absorbs water and mineral salts. Scales protect the thallus from desiccation in unfavorable environments. Aquatic species of Riccia lack scales.