Gonium largely independent of the supply of elaborated organic food from the thallus of the mother plant (the gametophyte).
In many Laminariaceae the thallus also grows regularly in thickness by division of its surface layer, adding to the subjacent permanent tissue and thus forming a secondary meristem.
We may note the universal Li occurrence on the lower surface of the thallus of fixing ver and absorbing rhizoids in accordance with the terrestrial Worts.
Indeed the genus Oedogonium exhibits a high degree of specialization in its reproductive system, considering that its thallus has not advanced beyond the stage of an unbranched filament.
I, Germinating ascospore (sp) 2, Thallus in process of formawith branching germ-tube tion.
Most systems agree in deriving the major divisions from the characters of the reproductive organs (perithecia, apothecia, or basidiospore bearing fructification), while the characters of the algal cells and those of the thallus generally are used for the minor divisions.
In Desmarestia and Arthrocladia, for example, it is found that the thallus ends in a tuft of such hairs, each of them growing by means of an intercalated growing point.
In Fucaceae, Dictyotacea, and in Laminariaceae and Sphacelariaceae, among Phaeosporeae, the thallus consists of a true parenchyma; elsewhere it consists of free filaments, or filaments so compacted together, as in Cutleriaceae and Desmarestiaceae, as to form a false parenchyma.
In the great majority the thallus is obviously filamentous, as in some species of Callithamnion.
E, Pleurococcus Sp. (Cystococcus) from the thallus of Cladonia furcata.