90 CONFERVACE.E. 



2. HoRMOTRiCHUM horeak, Harv. ; filaments slender, forming decumbent strata of a 

 pale yellowish-green, flaccid, slightly interwoven ; articulations as long as broad or 

 somewhat longer, at length constricted at the nodes. 



Hab. On rocks near high-water mark. Whalefish Islands, Davis's Straits, Dr. Lyall. 

 (v. s. in Herb. T.C.D.) 



This forms a thin, yellow-green, decumbent fleece, lying on the surface of the rock, 

 and extending indefinitely. Filaments flaccid, glossy when dry, variously interwoven, 

 about half the diameter of those of H. Toimganum, but in other respects very similar, 

 except that the cells are commonly shorter. Articulations usually quadrate ; in age 

 contracted at the nodes. 



A much more slender plant than H. Younganum, softer, more glossy, and spreading 

 in patches, not tufted. 



3. HoRMOTRiCHUM speciosum, Carm. ; filaments long, thick, flaccid, straight, at length 

 curled, the margin slightly crenate, forming bright yellow-green strata, glossy when 

 dry ; articulations half as long as their breadth, the cell-wall very thick. Hai'v. Phyc. 

 Brit. t. 186, B. Wyatt, Alg. Damn. No. 196. (Lyngbya.) 



Hab. Mixed with the foregoing species, at Whale-fish Islands, Dr. Lyall. 



Much more robust than the following species, to which it is allied. 



4 HORMOTRICHUM Carmichaelii, Harv. ; filaments scarcely capillary, closely inter- 

 woven into decumbent, crisped, full-grass-green strata, variously twisted ; articulations 

 half as long as their diameter ; the cell-wall thick. Harv. Phyc. Brit. t. 186. ^. Wyatt, 

 Alg. Damn. No. 230. Kiitz. Sp. Alg. p. 382. 



Hab. On rocks and fuci, between tide marks. Near Boston, Mr. Calverley. In a 

 "running stream" (quere, of salt, or fresh water?) on stones, in Wellington Channel, 

 Arctic Regions, Dr. Lyall. (v. v.) 



Strata extensive, densely interwoven, full green, or somewhat yellowish, soft, but not 

 gelatinous, and not glossy when dry. Filaments very long, thinner than human hair, 

 variously curved and twisted. Articulations shorter than their diameter, generally 

 less than half as long as their breadth ; the cell-wall thick, and the endochrome at 

 length contracting into a lenticular sporidiuai. 



This {)lant is common on the British Coasts, where it occurs between tide marks. 

 The specimen received from Mr. Calverley is said to come " from fresh water near 

 Boston ;" but I suspect some mistake. Whether that from the Arctic Regions be from 

 brackish or fresh water I cannot tell ; but under the microscope there is no character 



