1914] 
SCHRAMM—PURE CULTURE METHODS IN THE ALGJE 39 
one season оп soil in the greenhouses. Тһе vegetative cells 
when placed in water readily produce zoóspores, and isolations 
were made from these with little difficulty. Unlike Botrydium, 
this form grows exceedingly well on the mineral nutrient agar. 
BACILLARIALES 
The diatoms were encountered only incidentally in connec- 
tion with other forms, and no particular effort was made to 
isolate forms in pure culture. Although diatoms, in general, 
have a gelatinous exterior, a small Navicula was on several 
occasions obtained in pure culture and grown successfully. 
It should be said, however, that the great majority of diatom 
colonies obtained were contaminated with bacteria. 
CYANOPHYCEJE 
In the class Cyanophycee, the most difficult problems of 
isolation are met. Тһе almost universal presence of an abun- 
dance of external mucilaginous material, the complete ab- 
вепсе of ciliated reproductive cells, and the virtually complete 
absence of free, endogenous spores, renders the technique 
particularly difficult. Тһе gelatinous investments аге, in 
all cases investigated, impregnated with bacteria which can- 
not be completely removed by the most vigorous washing. 
Among the forms studied were Aphanocapsa, several species 
each of Oscillatoria, Nostoc, and Anabena, Cylindrospermum, 
and Microcoleus. Of these, only two species, one of Oscilla- 
toria and one of Microcoleus, were obtained in pure culture. 
In the isolation of these two forms, silicic acid jelly was found 
to be indispensable. While directions for preparing this 
medium are to be found in many places in the literature, certain 
difficulties encountered in its preparation have made it desirable 
to give at this time, and in some detail, the method used. 
As regards the preparation and mixing of the sodium silicate 
and hydrochloric acid solutions, the directions given by Smith 
(22) may be followed. It is only necessary to point out in 
this connection that if Merck’s “sodium silicate pure crystals" 
is used, the solution should be made up with cold water. If 
hot water is used, an unidentified substance (insoluble in cold 
water) goes into solution, and frequently causes the coagulation 
