82 SPECIES OF DESMIDS. 



a. Mucous masses floating; cells 2-2^ times longer than wide, 



Braunii* 31 

 a. Mucous masses mingled with filamentous algse; cells 3-4 times 



longer than wide . . Endlicherianum, 32 



a. Mucous masses on wet rocks and mosses; cells 2-3 times longer 



than wide clepsydra, 32 



II. SPIROT^ENIA. FIG. II 



i. Spiral band single (a). 



i. Spiral bands more than one obscura, 33 



a. Cell 8 to 10 times longer than broad condensata, 33 



a. Cell 4 times longer than broad . bryophila, 33 



12. PENIUM. FIG. 12. 



i. Chlorophyll interrupted by i central transverse band (a). 

 i. " " " 3 transverse bands; cytioderm smooth, 



inter ruptum, 35 



1. " " " " " " cytioderm spirally 

 striate spirostriolatym** 



2. Chlorophyll concentrated into 2 or more nuclei; in mucus, crassa, 37 



3. " diffused (b). 



a. Ends truncate, square truncatum, 35 



a. Ends not truncate; cells slightly constricted, sides straight, 



minutum, 35 

 a. " " " " " " sides convex, 



cruciferum** 



a. " " " cell not constricted, 3-5 times longer than 

 wide digitus, 34 



a. Ends not truncate; cell not constricted, 5-6 times longer than 



wide closterioides, 35 



b. Cytioderm smooth (c). 



b. " with pearly granules in longitudinal rows, 



margaritaceum, 34 



c. Cells in mucus, diameter -^ to -^ in. (63-83^) 3 to 4 times as, 



long as wide oblong um, 34 



c. " " " about twice as long as wide . . . rupestre, 37 

 c. " " " more than 3 times as long as wide . Brebissonii, 36 



c. Cells not in mucus; each semi-cell a truncated cone . tumidum** 



d. Cells oblong, often slightly constricted .... lamellosum, 34 

 d. Cells subcylindrical, in families of various sizes intermingled, 



polymorphism, 36 



d. Cells subcylindrical, not in families Jenneri, 36 



d. Cells broadly fusiform, 4-5 times longer than wide, navicula, 36 



**J. R. M. S., Feb. '89. 



