IS6 FRESH-WATER BIOLOGY 



iSS (132, i37> 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. 



/^•^?S^^t^^ C^'^oraa.toph.oKi without pyrenoids; zoospores amoeboid, with 



fS -"^^i^ \ B ^ single cilium, a pigment spot, and one (sometimes two) chroma- 



Wi^&W&l ^^5!%, tophores; frequently they germinate within the mother-membrane 



%*'#*^^ , ^^\ without a motile period. 



J* ^l C^»^ Fl*'- 189. Botrydiopsis eriensis Snow. a. vegetative cell; b. zoospores. 



" ^ ^<iiSX__^ Xs8o. (Original.) 



158 (157) Chromatophore single 159 



159(160) Chromatophore parietal Chlorococcum Fries. 



Chromatophore with a circular opening and a pyrenoid; zoospores 

 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 

 placed in a different genus. 



Fig. 190. Chlorococcum in/usionum Rabenhorst. a. vegetative cell. 

 A B 6. zoospores. X 625. (Original.) 



160 (159) Chromatophore central with radiating strands. 



Radiosphaera Snow. 



^M£ifyy\ ''^S' "^ Except for the nature of the chromatophore this genus 



.;^^^sviif^\\ ^ \ resembles Chlorococcum, but at the center is a pyrenoid 



\\, -fty^i»5''S*) 1 4 C^ from which the chromatophore radiates. Zoospores 



"'"'^^^' ■// \^, \[| Q^ with two cilia and a pigment spot are formed. 



I I \ \^ — ^^'^' ^^^' R^iosplmera sp. Snow. a. vegetative cell; 



\ [ \ ^' 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 increase of water bi-dliated 

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

 produce star-shaped zygospores. 



Fig. 192. Protosiphon botryoides Kl&hs. X 75. (After Klebs.) 



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



jections 164 



