1172 Wisconsin Academy of Sciences, Arts and Letters. 
different species. This is especially true in the case of the 
Cyanophyceae. 
The algae do not form colonies of characteristic appearance 
so that the species cannot be determined by macroscopical exam¬ 
ination. I have not found a report by any investigator who 
was able to determine his alga before isolating it in pure cul¬ 
ture. In my attempt to isolate as many forms as possible, the 
determination of the species in plate cultures containing a mix¬ 
ture of forms has been very important. The method used was 
to cut out a colony from the agar with a sterile needle and 
mount it on a sterile slide and under a sterile cover glass. A 
microscopical examination could then be made and the species 
determined. In this manner two to three hundred colonies 
could be examined in a day and perhaps only twenty of them re¬ 
tained for further study, thus saving the time necessary to trans¬ 
fer all colonies to an agar slant and to allow them to grow be¬ 
fore determining the species. 
If the alga on the slide was a species that was desired for 
further study, it was plated again by removing the cover glass 
from the slide and mixing the crushed colony with a drop of 
melted agar. This melted agar was then transferred to a tube 
containing melted agar and the whole mass plated again. The 
disadvantage of this method is that there is a loss of time in 
waiting for the second Petri dish culture to grow, and a danger 
of infection from the various manipulations. There is un¬ 
doubtedly some chance for bacterial infection from the slide 
and also in transferring the colony to the melted agar, but 
this is small enough to be neglected. The distinct gain from this 
method is that in case the culture is slightly infected in the ori¬ 
ginal Petri dish, the replating is apt to separate the bacteria 
from the algae, while a slightly infected colony put on a agar 
slant would prove a total loss. The method described above is 
especially valuable in the case of the rarer algae. My results 
show a distinct saving in the total time required for manipula¬ 
tion by the method here described, but if one wishes to obtain 
a pure culture of an alga, irrespective of the particular species, 
