19141 
SCHRAMM—PURE CULTURE METHODS IN THE ALG 97 
tube of sterile mineral nutrient solution. Although the great 
majority of such isolations remained bacteria-free, the zoóspores 
failed to develop, and finally died. It is only necessary, there- 
fore, to find some medium in or on which the zoóspores will germ- 
inate and develop into plants, to effect а pure culture of 
Vaucheria or Oedogonium. Bulbochete was not used, but in 
all probability this form will lend itself to a similar technique. 
Conjugales.—Thus far it has not been possible to obtain 8 
pure culture of any member of the Conjugales. Тһе repre- 
sentatives of this order, in their vegetative phases, are provided 
throughout with an exterior gelatinous investment which is 
very generally impregnated with bacteria. АП attempts to 
obtain pure cultures from vegetative individuals failed. Fur- 
ther, there is a complete absence in the order of motile spores 
and, in general also, of separable, asexual, endogenous spores. 
The zygospore, therefore, suggests itself as а possible means 
of solving the problem, especially in those forms where it is 
produced endogenously, and where it does not subsequently 
coalesce with the wall of the gametangium. While pure 
cultures were not obtained from these, the method used in 
Spirogyra setiformis is of interest and may prove serviceable 
in the ultimate isolation of these forms in pure culture. 
Filaments containing mature zygospores, but in which the 
zygospore-containing cell walls were still completely intact, 
were washed repeatedly in sterile water and then broken up 
as thoroughly as possible with needles; in this process, numer- 
ous zygospores were freed from the enclosing walls, later to be 
taken up with sterile pipettes, and transferred to sterile drops 
of water. Each zygospore was subsequently transferred from 
ten to twenty times to fresh, sterile water drops, and finally 
taken up with a sterile pipette. When a considerable number 
of zygospores had thus been isolated, they were introduced into 
a tube containing a few cc. of sterile water, vigorously shaken, 
and the entire contents poured out into a Petri dish containing 
a layer of sterile nutrient agar. After rocking the dish for a 
short time, it was allowed to remain quiet until the zygospores 
had settled down on the surface of the agar. The free water 
was then very slowly and carefully, but completely, drained 
from the surface of the agar, and the plate allowed to remain 
