64 
Bristol ’ — (9/z the Algo-Flora of some Desiccated 
doubt, however, as to the identity of the alga. The heterocysts were usually 
oval, 5 to 6 n broad by 7-5 to 8 -5 /x long, but occasionally they were sub- 
spherical, about 6 to 7*5 /x in diameter. 
19. Cylindrospermum muscicola , Kuetz. (Text-fig. 7 b). 
In two of the soils a blue-green alga was found which agreed very 
nearly with this species, though it differed in certain respects. The 
vegetative cells were 3*5 to 4 /x broad, but were either equal in length or 
somewhat shorter than broad ; one or two conspicuous clear 'granules were 
observable in each cell. The heterocysts were oval and mostly 4 to 5 ju 
broad and 5 to 8-5 jx long, though they might be longer, while the spores 
were cylindrical-oval, 9 to 10*5 broad and 17*5 to 24 /x long, with smooth 
golden-brown walls. 
At b in Text-fig. 7, B, is shown an abnormal filament in which the spore 
had begun to develop at a little distance from the heterocyst instead of 
adjacent to it. The species is here recorded for the first time from Great 
Britain. 
20. Cylindrospermum marchicum , Lemm., forma tenue , n.f. 
In Text-fig. 7 , A, is figured a blue-green alga very closely resembling 
C. marchicum in all its general characters, but differing from it considerably 
in point of size; this form was observed in the cultures of only one soil. 
The vegetative cells were cylindrical, 1*5 to 2 /x broad and 3*5 to 6 /x long, 
Text-fig. 7 . a. Cylindrospermum marchicum , Lemm., forma tenue , n.f. h., heterocyst; 
s., ripe spores; y.s ., young spores in series; vegetative cells. B. Cylindrospermum muscicola , 
Kuetz. a., typical filaments in different stages of spore-formation ; b ., spore formed in an irregular 
position, x 825. 
filament was conical. Only very few heterocysts were observed, but they 
were subspherical, about 2*5 /x broad and 3 /x long. The spores were 
cylindrical, with smooth colourless walls, and 4 to 4-5 /x broad by 9 to 11 /x 
long ; they grew in series of three or four together. The extremely 
elongated vegetative cells and the seriate spores with colourless walls 
