94 
B. Muriel Bristol. 
presence of free-floating unicells. In December, 1916, blue-green 
algae appeared from the Broadbalk and Hoosfield soils, forming 
strata below the surface of the liquid, usually attached to the soil, 
but later extending up the glass sides of the vessel. The colours 
of these strata varied very much not only with the species but also 
with their state of development; young strata were usually a light 
blue-green, but at later stages they became olive-green or even 
brownish-black. When once they had begun to develop, the blue- 
green algae grew much more rapidly than the green algae until 
eventually they very strongly predominated in the cultures. 
A considerable time elapsed before the identity of the various 
forms could be established, since it was necessary in most cases to 
follow the complete life-history of the alga before it was possible 
to arrive at a definite conclusion ; little or no imformation could be 
obtained from the developmental stages which at first predominated. 
In the final identification of the species considerable difficulty has 
been experienced, in that many of the forms found in the cultures 
do not agree exactly with any of the species previously described, 
though bearing a very strong resemblance to one particular type. 
In these cases it has been necessary to take into consideration not 
only the somewhat abnormal conditions under which the algae have 
been growing in the cultures, but also the extended period of 
drought which they had experienced before being introduced with 
the soil into the culture. Where the differences might be 
ascribed to one of these two causes, the form under consideration 
has been referred to the particular species which it most nearly 
resembles, a special note being made of the distinctions between 
the two forms. 
II. Rhsults op Cultural Experiments. 
Alga Found, 
Chlorococcum huinicola (Naeg.) Rabenh. 
Nostoc muscorum Kiitz. 
Anabcena oscillarioides Bory 
var. terrestris (n. var.) forma major. 
Plectonema Battersii Gomont. 
Hapalosiphon flexuosus Borzi forma (?) 
Chlorococcum humicola (Naeg.) Rabenh. 
ffostoc muscorum Kiitz. 
A fame cf 
Plot. 
Broadbalk 
Date of 
Collection. 
1893 
Broadbalk 
1881 
