HOW TO KNOW THE FRESH-WATER ALGAE 



Figure 195 



277a Setae bulb-like at the base. Fig. 195 BULBOCHAETE 



Fig. 195. a, Bulbochaete insignis Pringsh., 

 showing oogonium with oospore, and an 

 attached dwarf male plant; b, B. con- 

 gener Him; c, holdfast cell. 



Like its close relative, Oedogonium (Fig. 

 159) this genus contains numerous species 

 which are differentiated on the basis of di- 

 mensions and details of the reproductive 

 structures. They cannot be identified in 

 the vegetative condition. The branched 

 filaments are always attached (at least 

 when young) and are quickly identified 

 by the bulbous-based, unicellular setae 

 that develop at the anterior end of the 

 cell. They are to be sought on overhang- 

 ing grass, or on the culms of rushes, sub- 

 merged aquatic plants, etc. Most species have dwarf male plants 

 growing epiphytically on the oogania (female sex organs). 



277b Setae shaped otherwise , . . . 278 



278a Setae sheathed at the base. See Fig. 150 COLEOCHAETE 



278b Setae not sheathed at the base 279 



279a Thallus not embedded in mucilage, or if so, inclosed in a very 



soft watery mucilage without definite shape 280 



279b Thallus inclosed in a firm mucilaginous matrix of definite shape, 

 globular or somewhat elongate and irregularly arbuscular (some- 

 times strands 4-15 cm. in length). Fig. 196 CHAETOPHORA 



Fig. 196. a, Chaetophora elegans (Roth) 

 C. A. Ag., habit of thallus; b, C. in- 

 crassata (Huds.) Hazen, habit of thal- 

 lus; c, C. incrassata, portion of branch- 

 ing system. 



Microscopically, species of this genus 

 are delicately and gracefully branched 

 filaments that occur in macroscopic tufts 

 or gelatinous balls. One, C. incrassata 

 (Huds.) Hazen, is composed of cables of 

 elongate cells which give off laterally 

 dense tufts of dichotomous branches. 

 The resulting growth produces bush-like 

 or arbuscular thalli which may become 

 10-15 centimeters in length. Other spe- 

 cies form spherical or irregularly glo- 

 bose balls one or two millimeters in 

 diameter on submerged leaves (especially in cold water), wood, or on 

 cattail stems and are often gregarious so that extensive patches occur. 



Figure 196 



122 



