THE FRESH-WATER ALGAE 



157 



164 (165) Reproduction by zoospores: chromatophore of many radially- 



placed rods or segments united beneath the surface. 



Scotinosphaera Klebs. 



Zoospores fusiform; their production preceded by a 

 contraction of tile ciiromatopiiore to the center, about 

 which there is a granular substance; zoospores penetrate 

 some water plant or germinate in tiie water. 



Resting cells occur which have one or more thicken- 

 ings of the membrane. 



It was first found in the dead leaves and branches of 

 Hypniim, and its normal habitat is probably in the 

 tissues of some higher water plant, but it occurs fre- 

 quently in the water and may be cultivated with ease. 

 Fig. 193. Scotinosphaera paradoxa Klebs. X about 265. 

 (After Klebs.) 



165 (164) Reproduction by copulation of isogametes and in some cases by 



zoospores. ... 166 



166 (167) Chromatophore a parietal layer with many pyrenoids, later show- 



ing a network. Membrane with cellulose projections. 



Chlorochylrium Cohn. 



Cells spherical or slightly irregular; chromatophore 

 with many inwardly projecting portions containing 

 many pyrenoids. The zoospores are liberated singly; 

 the gametes escape together while still enveloped by the 

 inner lining to the membrane in which they copulate. 



Chlorochytriuvi occurs in the intercellular spaces of 

 Lemna. In some species a cellulose projection extends 

 to the surface of the epidermis at the point of penetra- 

 tion of the zoospores, but is not found in all. 



Fig. 194. Chhrochytrium lemnae K.\ehs. Cells in the tissues 

 of Lemna. X 500. (After Klebs.) 



167 (i66) Chromatophore dense, with many starch grains: membrane lamel- 



late . Endosphaera Klebs. 



Cells spherical or irregular, found in the tissue of water plants. 

 In reproduction internal divisions occur, giving rise to eight or sixteen 

 oval isogametes with two cilia and a pyrenoid. The zygospore pene- 

 trates into the intercellular spaces of Fatamogeton if it is present, but 

 ^''^ C dies if it cannot be found. 

 In the spring time it is found as large resting cells in the tissues 

 2iJ°V) of the dead leaves. 



\i Fig. 19s. Endosphaera biennis "KXehs. a. young cell; 6. gametes: c. union 



of gametes, a. X about igo; b, c. X about 400. (After Klebs.) 



168 (156) 161) Cells with a thin stalk-like projection on one or both ends, 



either free or attached 169 



169 (170) Cells free, linear, curved, or spiral, ends with a spine or stalk-like 



projection Ophiocytium Nageli. 



Chromatophore single, parietal, with no pyrenoid. Reproduction by 

 means of zoospores, eight of which are formed in a single cell and are 

 liberated by the end of the cell being thrown off like a cap. 



Though the habitat of Ophiocytium is the same as for a number of 

 other Protococcaceae, it is not so frequently found. When it does 

 occur, however, in a body of water it may be abundant. 



Fig. 196. Ophiocytium cochleare A. Braun. X 600. (Original.) 



170 (169) Cells similar, but shorter and attached 171 



^^ 



