The young
prothallus of both species is distinctly lopsided, and the asymmetry often persists until maturity.
For sample from Control Station, the thallus is olive green and
prothallus is bright white in colour.
Further studies on the
prothallus, embryo, and young sporophyte of Tmesipteris.
This species is characterized by a usually conspicuous black
prothallus and a diffusely areolate, dark grayish thallus.
This downward migration of the nucleus sets up an asymmetric first cell division, determining the developmental fate of the two daughter cells, one giving rise to the primary rhizoid, and the other giving rise to the
prothallus. Thus, in dictating the direction of nuclear migration, gravity also dictates the developmental polarity of the spore.
The first stages of
prothallus development lack mycorrhizal colonization even when rhizoids have developed (Fig.
The
prothallus bears the female (archegonia) and male (antheridia) organs.
Form of mature
prothallus: 0 = highly branched and vascularized; I = subterranean, elongate, and cylindrical; 2 = tuberous and subterranean; 3 = filamentous; 4 = branched and ribbon shaped; 5 = deeply lobed; 6 = cordate, may be branched; 7 = cordate, becoming ribbon like; 8 = highly reduced.