HOW TO KNOW THE FRESH-WATER ALGAE 



200a Cells quadrate, with 1 star-shaped chloroplast containing a single 

 pyrenoid. Fig. 140 SCH1ZOGONWM 



Fig. 140. Schizogonium 

 murale Kuetz. 



This species and 1 oth- 

 er, S. crenulafum (Kuetz.) 

 Gay with short, crinkly 

 filaments, are found in 

 the United States, grow- 

 ing on dripping rocks, or wet soil. The basically filamentous habit 

 may become expanded so that a frond-like thallus is produced. This 

 genus, together with Prasiola (Fig. 153) have sufficient structural and 

 reproductive characteristics to warrant placing them in a separate 

 family (Schizogoniaceae) and order (Schizogoniales). The star-shaped 

 chloroplast is helpful in making determinations. 



Figure 140 



200b Cells mostly longer than wide; 2 chloroplasts 201 



201a Chloroplasts 2-6 relatively small and biscuit-shaped or somewhat 

 star-shaped, connected in the midregion of the cell by a strand 

 of cytoplasm inclosing the nucleus; conjugating cells becoming 

 filled with layers of pectic substance; zygospores cushion-like, 



compressed spheroid, or subquadranguler. Fig. 141 



ZYGNEMOPSIS 



Fig. 141. a. Zygnemopsis decus- 

 sate* (Trans.) Trans., vegeta- 

 tive cells with cushion-like 

 chloroplasts; b, conjugation 

 to form zygospores; c, Z. des- 

 midioides (West & West) 

 Trans. 



The differences between this 

 genus and Zygnema occur 





Figure 141 



mostly within the reproductive 

 habit so that determination of 

 plants in the vegetative condi- 

 tion is not certain. The irregu- 

 lar, biscuit-shaped chloroplasts are not conspicuously star-shaped as 

 they usually are in Zygnema, a genus which is more commonly found 

 and which includes more species than does Zygnemopsis. 



92 



