HOW TO KNOW THE FRESH-WATER ALGAE 



115a Cells bearing a stout spine at either end. Fig. 90 



CLOSTER1DWM 



Fig. 90. Closteiidium lunula Reinsch. 



This species has two relatives which are 

 nearly straight. It can be differentiated from 

 Closterium (Fig. 86) by the fact that there is but 

 a single chloroplast, and by the absence of the 

 terminal vacuoles with vibrating granules. 



Figure 90 

 115b Cells without stout spines at the ends 116 



116a Cells inclosed in a mucilage (usually in clusters but sometimes 

 solitary); in some species the curvature is so great that the tips 

 nearly touch. See Fig. 56 K1RCHNERIELLA 



116b Cells not inclosed in mucilage (rarely in mucilage; see Fig. 67): 

 usually in clusters but sometimes found solitary; curvature of the 

 inner margin nearly that of the outer; tips of cell not almost touch- 

 ing. See Fig. 67 SELENASTRUM 



117a (109) Living in the tissues of higher plants or in animals 118 



117b Not living in tissues of plants or in animals 121 



118a Cells globose, numerous within protozoa, sponges. Hydra, et al. 

 Fig# 91 CHLORELLA 



Fig. 91. a, Chlorella (Zoochloiella) para- 

 sitica Brandt (in Ophrydium, a co- 

 lonial ciliate); b, C. (Zoochlorella) con- 

 ductrix Brandt (in Hydra); c, C. ellip- 

 soidea Gerneck, two cells enlarged 

 to show parietal chloroplasts. 



These small cells occur singly or in 

 gregarious masses, either free-living or 

 contained within the bodies of animals 

 such as protozoa and sponges. As en- 

 dozoic plants they are often known as 

 Zoochlorella. Species are not well-de- 

 fined and mostly are differentiated by size. The chloroplast is thin 

 and cup shaped. Like other members of the Chlorococcales, reproduc- 

 tion takes place by internal cell division (in this case forming non- 

 motile autospores). Chlorella is a genus that has been and is now 

 being used in culture for investigations of the" process of photosyn- 

 thesis and the synthesis of proteins. 



Figure 91 



65 



