106 SPECIES OF DESMIDS. 



aa. Apices of rays obtuse; diameter -g-J-g- to -^ in. (40-50;*), 



drachm, 129 



<za. diameter y^ to y^ in. (15-20;*), 



iotanum, 137 



aa. Apices of rays not obtuse 



bb. End of cell in front view papillose or verrucose (cc). 

 bb. " " not papillose nor verrucose (dd). 



cc. Diameter -^fa in. (36;*) or smaller, arcuatum, \-$Q\subarcuatum, 140 

 cc. -gfa to ffa in. (60-80/1) ; arms diverging, anatinum, 139 



dd. End view, sides straight, angles 3-4 spinous,, polymorphism^ 126 

 dd. " sides concave; arms long, straight, in front view di- 

 verging ........ ..... paradoxum, 129 



dd. End view, sides concave; arms short, Haabceliense, 131; nanum, 138 

 dk/. sides convex; arms short, tumid at base, Heleanum, 133 



^. Apices of arms inconspicuosly bifid or trifid, 



Haabotliensc, 131; paradoxum, 129 

 ee. Apices of arms prominently and deeply trifid . . . Osceolense* 



ff. Apices of arms obtuse; the arms mere lobes, very short, 



silatatum, 128 



ff. " arms long, narrow .... arachne, 129 



ff. Apices of arms bifid; front view end with a crown of papillae, 



Floridense, 135 

 ff. Apices of arms bifid; front view end without papillae, 



pentacladum, 136 



gg. End view 4, 5, 6, or y-angular or radiate (hJi). 

 gg. End view triangular ('). 



hh. Cytioderm rough with pearly granules; rays 4-7, short, obtuse, 



margaritaceum, 125 

 hh. granulate; end view 4-6 angled, sides straight, 



Meriani, 132 

 ////. end view 4 angled, angles with 2 spines, 



Nova CcesarecE, 145 



hh. end view 4-5 angled, sides concave, angles 



without spines ........... dilatatum, 128 



. Angles in front view notched or otherwise divided (jj). 



ii. Angles entire (kk). 



*Bulletin Torrey Botanical Club, Dec. 1885. 



