1901] EREMOSPHAERA AND EXCENTROSPHAERA 315 
agar agar (5 to 7 grams to the liter of nutrient solution) enabled 
one to keep perfect trace of the cells, and was more satisfactory 
for many reasons. Stender dishes were used for culture vessels 
because it was desirable to have as large an amount of the 
medium as possible, so that the cultures would last for some 
time, and in order that there might be a considerable surface for 
growth. The same precautions of sterilization were observed 
that would have been necessary for bacteriological work, and 
check cultures indicated that these methods were successful. 
Usually after sterilization there would be a considerable 
amount of moisture collected upon the surface of the agar, and 
it was in this fluid that the Eremosphaera cells were deposited. 
If placed directly upon the surface of the agar it seemed impos- 
sible for them to persist, but when transferred to the moisture 
and then gradually, through the evaporation of the superfluous 
liquid, brought in contact with the nutrient agar there was no 
difficulty in making them grow as well as in fluid media. 
Van Tieghem cell methods were not successful. The plants 
lived for a considerable length of time and the chlorophyll gran- 
ules moved under the influence of sunlight, but there was no 
development of any kind. Cultures kept in tightly sealed cells 
for several months would gradually present an appearance 
resembling the formation of spores, and at first this was thought 
to be the case. Upon investigation, however, it was found that 
this effect was due entirely to the rounding off of the chromato- 
phores, which were closely packed at the periphery of the 
sphere. Upon being restored to natural conditions such cells 
resumed the characteristic arrangement of the color bodies, and 
the nucleus at no time presented any other appearance than that 
found in the normal plant. 
Ward cells, which allowed a constant supply of air and yet 
prevented any contamination from the outside, were partially 
successful. The most satisfactory method for making direct 
observations of cultures, however, was to isolate a single individ- 
ual and place it on a slide either in sterilized water or a ines 
solution. A large cover-glass was then placed over it, being 
