HOW TO KNOW THE FRESH-WATER ALGAE 



282b Filaments not dichotomously branched; without constrictions. Fig. 

 199 VAUCHERIA 



Fig. 199. a, Vaucheria geminata (Vauch.) 

 De Cand., sex organs on a short pedicel; 

 b, V. sessilis (Vauch.) De Cand. 



Vaucheria usually forms dark green, vel- 

 vety mats on damp soil,, on rocks in flow- 

 ing water, or occasionally wooly mats 

 floating at the surface of ponds, having 

 broken away from their substrate. At ma- 

 turity the growths are 'dirty' green in color. 

 The siphonous filaments are large enough 

 to be seen individually with the unaided 

 eye. Several species are common in fresh 

 water, differentiated by shape and posi- 

 tion of the sex organs. The mats of Vau- 

 cheria harbor a veritable zoological garden of small animals. Long 

 considered to be a member of the Chlorophyta, this genus is now 

 classed with the Xanthophyceae in the Chrysophyta. 



283a (5) Chromatophores violet, gray-green or bluish-green, often ap- 

 pearing brownish in mass; mostly macroscopic Rhodophyta . . 284 



283b Chromatophores yellowish-green, carotin predominating, or some 

 other color than above 290 



284a Thallus macroscopic, spine-like, with node-like swellings, stiff and 

 cartilaginous, very little if at all branched. Fig. 200 . . . LEMANEA 



Figure 199 



Figure 200 



Fig. 200. Lemanea annulata Kuetz., habit of plant. 



This genus is a member of the Rhodophyta, but like other fresh 

 water red algae it is some other color, being gray- or olive-green. 

 The thalli are cartilaginous and stand erect from an attached base. 

 The slender, spine-like growths (up to 20 cm. in length), devoid of 

 branching make the plant easily recognizable. Species are differ- 

 entiated mostly on details of the reproductive structures. 



124 



