COLEOCH^ETE 



191 



(Fig. 183), and ChcetopJiora, are more 

 complex than Ulothrix, for they consist 

 of branching filaments of peculiar forms. 

 However, the cell structure, life his- 

 tories, methods of reproduction, and low 

 sexual conditions (isogamy) of these 

 types all show relationships to the Ulo- 

 thricacece. They are of especial interest 

 as leading up from the level of Ulo- 

 thrix to the highest form of the Con- 

 fervales, the genus Coleochcete. 



222. Coleochaete. Coleochcete (family 

 Coleochcetacece) contains a number of 

 species which live in fresh water, at- 

 tached to the stems and leaves of water 

 weeds, and they frequently appear on 

 the sides of aquaria. Some of the forms 

 are circular flat plates or cushions of 

 cells that really consist of systems of 

 filaments radiating out from a center. FlG - 184 - Cladophora 

 Large, two-ciliate zoospores are formed This large, much-branched, m- 



amentous alga, A, has many 



singly in the cells. The female organ, species common in both fresh 

 oogonium, is a large, flask-shaped cell 

 with a long neck (Fig. 185 A, o). Its 

 protoplasm forms a single spherical egg 

 which nearly fills the lower swollen 

 portion of the oogonium, and the neck 

 finally opens above to allow the en- 

 trance of the sperms. The male organs, 

 antheridia (Fig. 185, A, a), are small 

 cells, generally in groups, each of which develops a two-ciliate 

 sperm. 



and Draparnaldia are common on stones in clear brooks and in springs. 

 Cladophora (Fig. 184) is also a good type for laboratory study and yery 

 common. 



and salt water. Zoospores, 

 B, are formed generally 

 in terminal sporangia, and 

 there are gametes which fuse 

 in pairs, C, as in Ulothrix. 

 The older cells contain large 

 numbers of nuclei, and this 

 form, with certain relatives 

 (family Cladophoracese) , oc- 

 cupy a position somewhat 

 intermediate between the 

 Confervales and Siphonales 



