Rivularia] ALGiE GLOIOCLADE^. 393 



Ag. Syst. Alg. p. 26. — " Oscillatoria terpens, Bvry" (Arnott, 

 MSS.). 



On rocks and stones, in streamlets and the borders of subalpine 

 lakes. — " Fronds one-fourth or half an inch in diameter, circular, slightly 

 convex, sometimes greenish but oftener of a dark chestnut colour. M- 

 ter a time they run together into a flat spongy crust of indefinite size. 

 On the smooth face of a rock, exposed to the trickling of water, I found 

 a connected sheet of it, upwards of a foot in diameter. When broken, 

 the crust appears zoned within, so as to indicate the age of the plant, 

 each zone being equal to a year's growth. At this stage, it is always 

 more or less stony, from the absorption of calcareous matter." Carm. 

 MSS. 



7. R. granidifera, Carm. (gramdiferous Rivularia); frond 

 large convex becoming hollow underneath fleshy lubricous 

 brownish-olive, often including stony particles, (never petri- 

 fied.) — Linkia dura, y. Crustacea, Lyngb. Hgdroph. Dan. p. 197? 



On cliffs exposed to the trickling of water, common. " Annual," 

 Capt. Carm'uhael.—" Fronds from a line to half an inch in diameter, 

 often confluent, convex and at length concave underneath, fleshy, dusky, 

 olive-green and extremely slippery. Filaments rather thick, repeatedly 

 dichotomous. In the substance are generally enclosed a number of 

 stony particles. This species comes nearest in size and form to 7^. 

 calcarea; but is never, like that, petrified with calcareous matter ; the 

 fi laments are also much thicker and more decidedly branched ; and it is, 

 moreover, an annual plant, whereas the other exists for several years." 

 Carm. MSS. 



8. R. crusldcea, Carm. (incrusting Rivularia); crust very thin 

 widely spreading, filaments attenuated at the base fastigiately 

 branched above the middle olive-green. 



" On rocks, exposed to the spray of cascades in the hill-streamlets," 

 Cap/. Carmiehael.—" Crust of no determinate extent, extremely thin and 

 slimy, black. Filament* one-fourth of a line in length, attenuated at 

 the base, fastigiately branched above the middle, of an olive-green 

 colour." Carm. MSS. 



Sect. 2. ( Scytochloria, Harv.) : frond gclatinoso-coriav, <>>/<. 

 I, ,1ml and bullated or incrusting. Filament* closet densely ana 

 conspicuously cumulated, sit m a firm gelatine and pointing to- 

 wards tin periphery (not radiating). 



!». R. nitiila, Ag. (shining bullated Rivularia); frond Urge 



gelatinoso-eoriae i> lobed and plaited often bullated lubricous 



ihining deep-green, filaments simple or psendo-branched. — Ag. 

 Syst. Alg. p. 25. — Scytochloria nittda, Harv* MSS, — Rivularia 

 bullata, Berh. Alg. U 2./ 1. 



On rocks, in the m;i. Torquay, Mrs, Griffiths. Miltown Bfalbay, 

 jr. //. Hni vru. — Frondt subfoliaceous, tremelloid, tufted or gregarious, 

 much lobed, the lobes sinuous j in a young state, compressed, and tilled 

 with gelatine; in age becoming bullated and hollow ; from half an inch 



to :m null and half in diamet ST. Colour ;i deep but \cr\ vi\ id olive--! ten, 



lubricous and subgelatinoua to the touch. Substemce firm, elastic, not 

 easilj lacerated. Filamenti either simple or pseudo-brancbed, subtor- 



