English Soils: an Important Factor in Soil Biology. 59 
V. Descriptive Notes on tpie Species found. 
Myxophyceae. 
1 : Phormidium tenue , (Menegh.) Gomont. 
This species, found in twenty different samples of soil, is the com- 
monest blue-green alga in the soils examined. As observed in the cultures, 
it agreed exactly in dimensions and all other characters with the typical 
form from which the species was described. 
2 . Phormidium Bohneri , Schmidle. 
Up to the present time this species has been described only from 
damp soil in Africa, but there is no doubt that a Phormidium found grow- 
ing from four of these soil-samples must belong to this species. The algal 
filaments were almost' straight, but slightly curved and interwoven to form 
a thin pale blue-green stratum. The cells were usually a little shorter than 
broad, but might be of equal dimensions or rather longer than broad ; no 
constrictions were observed between the cells, and the end cell was generally 
rounded, though occasionally it was somewhat swollen and formed a knob- 
like termination to the filament. The sheath was colourless and rather thin, 
and the breadth of the filament about 2 1 u. 
3. Phormidium laminosum , (Ag.) Gomont. 
The alga identified under this name occurred in one soil only, but the 
extraordinarily varied habitat already described for this species makes the 
record an extremely interesting one ; there are few species of algae capable 
of living in places so widely different as hot springs, standing water, rocks 
moistened by spray from a waterfall, and garden-soil. The form observed 
in the cultures agreed almost exactly with the typical form, but the fila- 
ments were slightly wider, being 2 \x in breadth instead of only 1 *5 /x. 
4. Phormidium autumnale , (Ag.) Gomont. 
Next to P. tenue , this species occurred most frequently in the soils 
examined, having been found in the cultures of nineteen samples. The 
filaftients were interwoven to form expanded strata of a deep brownish-green 
or almost black colour on the surface of the soil and on the sides of the 
culture-vessel. The ends of the filaments were slightly tapering ; the end 
cell was sometimes capitate and sometimes rounded, and in this case the 
last two or three cells of the filament might be slightly curved. The breadth 
of the filaments was 4-8 /x. 
5. Lyngbya Kuetzingii, Schmidle. 
A blue-green alga very closely resembling this species was found in 
the cultures of seven of the soils, with usually straight but occasionally 
curved filaments matted together to form a dark brownish-green expanded 
stratum. The filaments were 3 to 3*5 broad, bounded by a strong colour- 
less sheath ; and the end cells were rounded without being tapering. Very 
