English Soils: an Important Factor in Soil Biology . 63 
14. Anabaena sphaerica , Born, et Flah. 
In the cultures of two of the soils a blue-green alga appeared which 
resembled this species more nearly than any other and is probably a form of 
it, somewhat larger than is typical. 
The vegetative cells were 5 to 6 jx or even as much as 8 [x broad, and 
shortly barrel-shaped. The heterocysts were spherical, 7 to 8-5 /x broad or 
smaller in young filaments. The spores grew in series on one side of the 
heterocysts, and had a smooth yellowish-brown wall ; they were oval and 
about 10 to 12 /x broad by 1 1 to 19 /x long when ripe. This species has not 
previously been recorded from the British Islands. 
15. Anabaena oscillarioides , Born., var. terrestris^ Bristol, forma minor. 
This alga occurred in five of the soil samples, but it has already 
been fully described and figured elsewhere, 1 hence no further particulars 
need be given here. 
16. Anabaena sp. ? 
In the cultures of three of the soils an Anabaena was found which, 
owing to its imperfect development, could not be identified with any of the 
described species. The vegetative cells were barrel-shaped, 5 to 6 /x in 
diameter and usually about 4 /x long, though they might be rather longer 
than broad, and a thin mucous sheath could sometimes be seen surrounding 
the filament, the terminal cell of which was conical. 
Heterocysts were numerous throughout the length of the filament, and 
were yellowish in colour and subspherical, about 8 /x in diameter, or even 
occasionally up to 9-5 fx. The spores were formed apart from the hetero- 
cysts, either singly or in short series of two or three, and when fully ripe 
appeared to be oval-cylindrical and about 11 to 12/x broad by about 27 /x 
long, with a smooth brownish spore-wall. There was, however, so much 
variation in the size of the spores that it was impossible to decide which 
species the form most closely resembled. 
17. Cylindrospermum majas , Kuetz. 
This alga was found in two soil-samples, and except for the some- 
what small size of the spores was quite typical of the species. The 
vegetative cells were 3-5 to 4 /x broad and 4 to 5 /x long ; the heterocysts 
elongated, about 5-5 to 6/x broad and 6-5 to 10 /x long; and the spores 
solitary, with a papillose, dark greenish-brown wall, about 11 to 12 /x broad 
and 18 to 22 /x long. 
18. Cylindrospermum lichenijorme , (Bory) Kuetz. 
This species was found in the cultures of four soils. Vegetative 
filaments were only rarely seen, and when found the cells appeared to be 
somewhat large for the species, about 4*5 to 5/x in diameter and a little 
longer than broad. The very characteristic spores, 11 to 14 \x broad and 24 
to 36 fx long, with their dark red-brown walls and truncate apices, left no 
1 Bristol, B. M.: loc. cit., 1919. 
