142 



FRESH-WATER BIOLOGY 



60 (64) In conjugating the whole of the contents of the conjugating cells 



passes into the zygospore. Subfamily Zygnemeae . . 61 



61 (62, 63) Chromatophores two, axial, star-shaped; a pyrcnoid in the center 



of each Zygnema de Bary. 



Conjugation either ladder-like or lateral: Zygospore within one of the conjugating cells, 

 or in the conjugating lube. According to Collins aplanospores may take the place of zygo- 

 spores, also resting akinetes with granular contents and thickened membrane may be found. 



Fig. 137. Zygnema sp. X 600. (Original.) 



62 (61, 63) Chromatophore one to several parietal, spiral bands, with many 

 pyrenoids Spirogyra Link. 



Conjugation ladder-like or lateral. Zygospore in one of the conjugating cells. Parthenospores 

 may be formed. 



Fig. 138. Spirogyra crassa Kiitzing. a. conjugation of filaments, b. zygospores X 100. (Original.) 



63 (61, 62) Chromatophore an axial plate, with several pyrenoids. 



Debarya Wittrock. 



Cells long; conjugation ladder-like; zygospore between the con- 

 jugating cells; the middle layer of the spore membrane yellow, with 

 three parallel longitudinal grooves, connected by radial striations. 



Fig. 139. Debarya glyptosperma Wittrock, showing two zygospores. X 95. 

 (After de Bary.) 



64 (60) In conjugation only a portion of the contents of the conjugating cells 

 passes into the zygospore. 



Subfamily Mesocarpeae . . 65 



