BRITISH DESMIDIEiE. 141 



any difference in the endochrome at that part. The spines, which are almost 

 confined to the angles, are irregular, some simple and some branched. The 

 end view has three or fovir broad and very irregular lobes ; these are spmous 

 and more or less emargmate, and frequently one lobe is much broader and 

 more spinous than the others. The spines on each lobe form two groups 

 separated by the notch ; they vary much in size, and are either simple and 

 subulate or else forked ; sometimes the forked spines are again di^•ided at the 

 apex. 



Staurastrum eaorme is by far the least symmetrical plant in this family, 

 especially in its front view, and it is very difficult to trace any di\-ision into 

 segments. 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 of frond ^iy of an inch ; breadth of lobe in the end \-iew y^Vr* 

 Tab. XXXIII. fig. 11. a, b, c. front -\-iews ; d, e. end views. 



tttt Spines numerous, conspicuous ; angles in end view either rounded, 

 acute, or extended into processes. 



34. S. spongiosum (Breb.) ; segments semiorbicular, spinulose; spines 

 forked ; end view triangular, bordered with forked spines ; angles 

 rounded. 



Staurastrum spongiosum, Brebisson, Meneghini, Synop. Desmid. in Linncea 



1840, p. 229. Brebisson, in lit. cum icone. 

 Desmidium ramosum, Ehrenberg, Verbreitung iind Ei)\/luss des mih'osko- 



pischen Lebens in Sild- und Nord-Amerika, t. 4. f. 21 ? (1843). 



Penzance and Dolgelley, rare, J. R. Ashdowu Forest, Sussex, Mr. Jenner. 

 Falaise, Brebisson. West Point, New York, Bailey. 



Frond large, about the size of that of Staurastrum muricatum, thickly 

 covered wdth short spines, which are forked at the apex ; segments semiorbi- 

 cular, having on each side one spine more conspicuous and more forked than 

 the rest. End A-iew triangular, fringed with short notched spines ; the sides 

 are slightly convex and the angles rounded. 



Staurastrum spongiosum is a very distinct species. In the front view it 

 has some resemblance to Xanthidium armatum, but is much smaller. 



Length of frond from -^^ to ^-j-g of an inch ; breadth from -g^r ^^ -^ ; 

 breadth at constriction from -^^ to y^-g. 



Tab. XXIII. fig. 4. a, b. front views ; e. end view. 



35. S. controversum (Breb.); frond spinulose ; segments with a 

 short process on each side terminated by minute spines ; end view 

 with three or four distorted rays. 



Staurastrum controversum, Brebisson, Meneghini, Synop. Desmid. in Linncea 

 1840, p. 228. Breb. m lit. cum icone. 



