156 FRESH-WATER BIOLOGY 



155 (132, 137, 174) Reproduction by the formation of zoospores only, or by 

 isogametes Family Protococcaceae . . 156 



156(161, 168) Cells spherical 157 



157 (158) Chromatophores many, parietal Botrydiopsis Borzi. 



/^^^1?xC/"^ Chromatophores without pyrenoids; zoospores amoeboid, with 



itfJ^:5rSs*Sr4, V B ^ single ciHum, a pigment spot, and one (sometimes two) chroma- 



l^i^Kl^; V^say tophores; frequently they germinate within the mother-membrane 



%'^^^^ ^^^ without a motile period. 



^1 mo^ Fig. 189. Botrydiopsis eriensis Snow. a. vegetative cell; b. zoospores. 



^ ^ ^^^X^^ Xs8o. (Original.) 



158(157) Chromatophore single i59 



159 (160) Chromatophore parietal Chlorococcum Fries. 



^y- Chromatophore with a circular opening and a pyrenoid; zoospores 



^ I g^ oval, with two cilia, a pyrenoid, and a pigment spot. Aplanospores 



may' form from non- liberated zoospores. An undescribed form 



^ which greatly resembles Chlorococcum has isogametes. It should be 



Y placed in a different genus. 



§ Fig. 190. Chlorococcum infusionum Rabenhorst. a. vegetative cell. 



AS *• zoospores. X 625. (Original.) 



160 (159) Chromatophore central with radiating strands. 



Radiosphaera Snow. 



"^ /^7\ '^-\ Except for the nature of the chromatophore this genus 



\ resembles Chlorococcum, but at the center is a pyrenoid 



i^'^' Q\ from which the chromatophore radiates. Zoospores 



If vt cs^. with two cilia and a pigment spot are formed. 



A "^ "^^ 

 ^ \ l\ y — Fig. 191. Radiosphaera sp. Snow. a. vegetative cell; 



A V I \ ^ *• zoospores. X 580. (Original.) 



B 



161 (156, 168) Cells more or less irregular, elongated, or tubular. ... 162 



162 (163) Cells free, more or less inflated or tubular, usually with a long, 



colorless cylindrical portion Protosiphon Klebs. 



Chromatophore a parietal, net-like layer, with pyrenoids. Under conditions threatening 

 drought, red resting spores are formed. In absence of light or mcrease of water bi-ciliated 

 zoospores are formed which on coming to rest produce spherical cells, or they may copulate and 

 produce star-shaped zygospores. 



Fig. 19a. Protosiphon botryoides Klebs. X 75- (After Klebs.) 



163 (162) Cells endophytic, rarely free, irregular, often with cellulose pro- 

 jections 164 



