DESMIDS, DIATOMS, AND FRESH-WATER ALG^E. 79 



Fig. 2i. Closterium acer6sum. 



row, longitudinal bands ; chlorophyl globules nu- 

 merous ; vacuoles near the ends ; cell very large. 

 C. Lunula, Fig. 25. 



Fig. 25. Clost6rium Luunla. 



d. Ends rounded ; chlorophyl often arranged in nar- 

 row, longitudinal bands ; chlorophyl globules of- 

 ten numerous ; vacuoles close to the ends. C. 

 Elireiibergii, Fig. 26. 



Fig. 2C. Closterium Ehrenbergii. Fig. 2T Closterium acnminatmn. 



e. Large, crescent - shaped ; centre broad, ends acute, 

 vacuoles small. C. acumindtum, Fig. 27. 



e. Small, crescent-shaped, distance between the ends 

 about ten times the central diameter; centre nar- 

 row, vacuoles indistinct. C. Didnce, Fig. 28. 



Fig. 28 Closterium Diauae. Fig. 20 Closterium Veuus. 



e. Very small, crescent-shaped, eight to twelve times 

 as long as broad ; centre narrow, ends sharp, 

 vacuoles distinct. C. Venus, Fig. 29. 



