270 NEMATOGEN.E. 



Conferva distorta, Dill. Conf., t. 22, /. A. E 

 Calothrix distorta, Harv. Man. 158. Mack. Hib. 237. 

 Elisa distorta, Gray. AIT. i., 282. 



In ponds and lakes. 

 Plate CIX. fig. 3. Portions of Trichomes x 400. 



Tolypothrix cirrhosa. (Carm.} 



Floating csespitose, olive, or blue-green, becoming brownish ; 

 trie-homes nearly simple, rather stout, distinctly articulate, 

 pallid blue-green, joints finely granular, one-half or one-third 

 as long as broad; sheaths moderately narrow (rather broad in 

 some of the older trichomes), indistinctly lamellose, smooth ; 

 heterocysts scattered. 



SIZE. Trichomes 012-'014mm., with sheath -02--025 mm. 



Scytonema cirrhosum, Garni. Eng. Fl. v., 366. Harv. Man., 

 155 (not of Eng. Bot. ii., t. 2920). 



Arthronema cirrhosum, Hass. Alg. 238, t. 68, f. 7. Rabh. 

 Alg. Eur. ii., 267. 



In mountain lakes. 



" It forms flexuous tufts of brown, very slender threads, proceeding in 

 fascicles from membranous sub-erect sheaths, and containing a single 

 row of cells scarcely so long as broad." Carm. 



Plate CV11I. fig. 3. Portions of trichomes X 400; a, hormogone 

 X400. 



APPENDIX. 



Although included by Thuret and Bornet, and also by 

 Kirchner, with Alga3, it can scarcely be doubted that all the 

 members of the genera Stigonema (or Sirosiphori) and Hapalo- 

 siplion must be transferred to the Lichens. They are included 

 here in the form of an appendix, for the satisfaction of students, 

 who would naturally expect some reference to them in a work 

 of this kind. At the same time we have availed ourselves of 

 the opportunity to add figures, and descriptions, of two or three 

 uncertain species, which have been recorded as British, under 

 new and unknown genera. 



GENUS 111. STIGONEMA. Ay. (1824.) 



Cells of the trichome often geminate or ternate, in conse- 

 quence of their lateral multiplication, or even forming trans- 

 verse, several-celled bands. Sheath large. Ceils surrounded 

 with a thick membrane, very prominent in the old filaments. 

 Hormogones originating in lateral branchlets formed of a single 

 row of cells. 



