COLEOCHAETE 



313 



tion the oospore forms four zoospores, each of which develops a 

 new filament. In some forms of Oedogonium there are both 

 male and female filaments. In some species the male plants are 

 miniature filaments and attach themselves to the female plants, 

 where they produce sperms in their terminal cells. 



Coleochaete. This form (Fig. 269), found growing attached 

 to water plants, has a disk-shaped plant body and also presents 

 some new features in connection with its reproduction. Like 

 Oedogonium it reproduces by zoospores and sexually by oospores. 

 One of the new features is 

 the development of a case 

 around the oospore by the 

 adjacent cells. This fea- 

 ture suggests a close rela- 

 tionship of this form to the 

 higher Algae, where the 

 formation of a case around 

 the immediate product of 

 the oospore is a prevalent 

 feature. The second new 

 feature is that the oospore 

 upon germination develops 

 neither a plant nor zo- 

 ospores, but a structure 

 consisting of several cells 

 each of which develops a 



FIG. 269. Coleochaete scutata. A, the 

 plate-like plant body with two oogonia 

 developed (X 25) ; B, thick-walled oospore 

 surrounded by vegetative cells (much en- 

 larged) ; C, a much enlarged section through 

 the oospore and its jacket of sterile cells, 



showing the multicellular body produced 

 by the oospore, each cell of which pro- 

 duces a zoospore. From Nature and 

 Oltmanns. 



zoospore from which a new 

 plant arises. Thus between 

 fertilization and the de- 

 velopment of new plants, 



there is introduced a new structural stage and one that is char- 

 acteristic of higher plants. These new features with others have 

 led to the theory that the higher plants have evolved from Algae 

 of the type of Coleochaete. 



In having multicellular plant bodies and more advanced 

 methods of reproduction, the Confervales, as a group, show 

 advancement over the preceding groups. The plant body is a 

 simple filament, branched filament, or a disk-shaped structure. 

 Sexual reproduction, which is isogamous in the lower forms, 

 advances to heterogamy where the two kinds of gametes occur in 



