92 SPECIES OF DESMIDS. 



ee. Cells twice or more longer than wide (^). 

 ee. Cells less than twice longer than wide {gg). 



ff. Cells cylindrical, sides parallel (sometimes rounded); verrucse ob- 

 tuse . . . . amo!nu7u, 78 

 ff. " " " verrucae emarginate, in lines, 



elegantissimiim, 78 



gg. Semi-cells oval or elliptical . . tumidum, (>\; orthosticum, 78 



gg. •'■ semi-orbicular, tetraophthalmum, 75 ; intermedium, 75 



hh. Semi-cells pyramidal, end truncate; basal angles rounded, 



^ octkodes, 76; Botrytis, 74 



hh. Semi-cells oval or elliptical, approximate . . . trigonum*' 



margaritiferum, 'jc^; punctulatum, 74 

 hh. " " " remote, granulate, portiannm, 77 



hh. Semi-cells quadrangular, ends truncate; diam. -5'^ --gi^ (60-73/1),. 



conspersum, 75 

 hh. " " ends concave . . . retusum.* 



hh. " " diam. ^-^(30-45 /<), 



pseudobroomei, 86 

 hh. " " diam. ^^-^^15^(13-14/^), 



sphalerostichum. * 

 hh. Semi-cells subreniform, sinus widened and rounded inwardly, 



latum, 76; renifoi-me, 76; pardalis.* 

 hh. Semi-cells subspherical, approximate . . . orbiculatum, 77 



hh. Semi-cells hemispherical, remote; base flattened, excavatum, 77 

 a. Ends and sides with teeth; sinus narrow, widened outwardly; basal 



angles rounded . Brebissonii, 75 



a. Ends without teeth, sides with 10 to 20; sinus gaping, dentatum, 76 

 jj. Margins crenate; semi-cell semicircular, nuclei 2, end truncate, 



cruciatum, 81 

 jj " undulate; sinus widening outwardly, ho7nalodermum, 81 



jj. " " sinus not widening outwardly (M). 



^k. Cell longer than wide; diameter -5-^ to -jp^ in. (38-44//), 



sublobatum, 80 

 kk. Cells longer than wide, diameter yuVir to Y^wa '"• (22-25//), 



mai-garitum, 80 

 kk. Cell not longer than wide, end truncate . . retusum, 80 



//. Diameter -j-JL-j- in. (12//), end truncate; sides convex, often ob- 

 tusely angled centrally . . . Schliephanckeanum, 82 

 //. Diameter greater than (i2/() -j-oVo '"• (fn''n). 

 *F.-w. Algse, p. 25. 



