Desmidiem.'] iNFrsoRTAt animalcules. 267 



cesses ; deeply constricterl at the middle. End view \^dtll three blunt 

 angles. Length 1- 800th. 



Statteastkitm: aspenim. — Segments elliptic or somewhat cimeiform, 

 with minute spines, which on the outer margin are usually dilated 

 at the end, or forked. Sporangia orbicular; their spines twice 

 branched. 



Var. {a.) — -Angles in end view rounded. 



Var. {h.) prohoscideuin (Breb.) — Angles in end view prolonged into 

 short rays, terminated by minute spines. 



f f JSnd view acuteh/ triangular ; segments, in the front metv, with a 

 forked spine on each side, othericise smooth. 



S. avicula. — Segments with a forked spine on each side; each 

 angle, in end view, terminated by a mucro-like spine. Frond very 

 minute ; scarcely rough ; the constriction producing wide triangular 

 notches. The forked lateral spines of the front view mark the 

 species. Length 1-907. Yery rare. 



t f f Lohes in end view broad, emarginate or bipartate. 



S. enorme. — Irregular or quadrate, spinous; end view three to four 

 lobed; lobes broad, more or less emarginate or bifid, and terminated by 

 spines, which are either simple or branched In the end view the 

 broadly emarginate lobes, which, exclusive of the spines, are truncate, 

 afford a good specific distinction between it and any other species. 

 Length l-601th. 



f f f f Spines numerous, conspicuous ; angles in end view either 

 rounded, acute, or extended into processes. 



S. spongiosum. = Besmidium ramosum (Ehr.) — Large, thickly 

 covered with short forked spines ; segments semi-orbicnlar, having 

 on each side one spine more conspicuous, and more forked than the 

 rest. End view triangular, fringed with short notched spines ; 

 the sides slightly convex, and the angles rounded. Length l-500th. 

 to 1-41 8th. 



S. controversum. — Deeply constiicted, spinulose ; segments elliptic 

 or fusiform, with a short process on each side, terminated by minute 

 spines ; end view vnth three to four distorted rays. Perhaps a variety 

 of S. aculeatum. Length 1-9 72nd. 



S. aculeatum. ^=Desmidium aculeatum (Ehr.) — Spinulose; constrictioiL 

 deep, producing a broad triangular notch on each side ; segments 



1 2 



