280 NEMATOGESLE. 



Rivularia gxanulifera. Carmichael MSS. 



Frond large, convex, becoming hollow underneath, fleshy, 

 lubricous, brownish olive, often including strong particles. 



SIZE. Trichomes "006 mm. diam. at the base. 



Harvey in Eng. Flor. v., 393. Harv. Man. 151. Hass. Alg. 

 363, t. 55, f. 1,4. 



On cliffs exposed to the trickling of water. 



" Fronds from a line to half an inch in diameter, often confluent, con- 

 vex, and at length concave underneath, fleshy, dusky olive-green, and 

 extremely slippery. Filaments rather thick, repeatedly dichotomous." 

 Carm. 



Plate CXV. Jig. 1. Trichomes, from an original and authentic speci- 

 men, X 400 diam. 



Uncertain Species. 



Rivularia botryoides. Carmichael MSS. 



Fronds minute, aggregated, roundish, wrinkled, ferruginous, 

 cartilaginous. Trichomes dichotomous. 

 SIZE. Not stated. 

 Harvey in Eng. Flor. v., 392. Harv. Man. 150. 



In streamlets, attached to rocks and stones. 



" Fronds about a line in diameter, hemisphaerical, wrinkled and carti- 

 laginous, scattered, or running together like a bunch of grapes. Tri- 

 chomes cohering firmly, obscurely sti'iated, dichotomous. Colour when 

 fresh, black, on drying, darkly ferruginous." Carm. 



We have seen no specimen, and therefore can add nothing to the 

 above description. 



Rivularia Crustacea. Carmichael MSS. 



Crust very thin, widely spreading, filaments attenuated at the 

 base, fastigiately branched above the middle, olive green. 

 Harvey, Eng. Flora v., 393. Harv. Man. 151. 

 Lithonema crustaceum, Hass. Alg. 266, t. 65, f. 3. 



On rocks exposed to the spray of cascades. 



" Crust of no determinate extent, extremely, thin and slimy, black. 

 Filaments one-fourth of a line in length, attenuated at the base, fasti- 

 giately branched above the middle, of an olive-green colour." Carm. 



GENUS 115. ISACTIS. Thur. (1875.) 



Similar to Rivularia, from which it differs in the frond being 

 flattened, and in the filaments being erect and parallel, and not 

 radiating. 



