82 SPECIES OF DESMIDS. 



a. Mucous masses floating; cells 2-2 J^ 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^NIA. 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, 



interruptum, 35 



1. " " " " " " cytioderm spirally 

 striate spirostriolatum.** 



2. Chlorophyll concentrated into 2 or more nuclei; in mucus, crawfl, 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 -g-i-p- to -^^ in. (63-83/<) 3 to 4 times as, 



long as wide . . . oblongum, 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, 



polymorphum, 36 

 d. Cells subcylindrical, not in families . r . . . . Jenneri, 36 

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



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



