270 NEMATOGENE. 
Conferva distorta, Dill. Conf., t. 22, f. A. E 
Calothriz distorta, Harv. Man. 158. Mack. Hib. 237. 
Elisa distorta, Gray. Arr. i., 282. 
In ponds and lakes. 
Plate CTX. fig. 3. Portions of Trichomes x 400. 
Tolypothrix cirrhosa. (Carm.) 
Floating cespitose, olive, or blue-green, becoming brownish ; 
trichomes 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--014 mm., with sheath -02--025 mm. 
Scytonema cirrhosum, Carm. 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 CVIII. fig. 3. Portions of trichomes X 400; a, hormogone 
X 400. 
APPENDIX. 
Although included by Thuret and Bomet, and also by 
Kirchner; with Alga, it can scarcely be doubted that all the 
members of the genera Stigonema (or Sirosiphon) and Hapalo- 
siphon 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. 4g. (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. Cells surrounded 
with a thick membrane, very prominent in the old filaments. 
Hormogones originating in lateral branchlets formed of a single 
tow of cells. 
