314 BOTANICAL GAZETTE [NOVEMBER 
These concentric layers can occasionally be separated by crush- 
ing, but usually they are very compact. They project inward 
towards the center of the cell, and in case a second continuous 
wall is formed, it remains indented wherever these excrescences 
appear. As many as twelve secondary walls have been counted 
around a single sphere, and there seems to be no limit to their 
formation. ; 
CULTURE METHODS. 
A plant which has had as many developmental stages 
ascribed to it as Eremosphaera naturally necessitates the most 
careful application of pure culture methods. Consequently the 
cultivation of this plant was attempted as soon as it was pro- 
cured, and cultures have been kept running successfully for 
about three years. As it was not convenient to visit the original 
locality frequently, and to obtain fresh material in that way, it 
seemed best to maintain a number of gross cultures from which 
pure transfers might be made at any time. No trouble was 
experienced in this, and water from the original pool, containing 
diatoms, numerous filamentous algae, and Eremosphaera, has 
been kept continuously in the laboratory. Bacteria appeared 
for a short time, but the water soon cleared, and all the algae 
have maintained themselves in good condition. These gross 
cultures were kept either in crystallizing dishes or wide-mouthed 
bottles, over which was a sheet of glass to prevent too rapid 
evaporation. It was found that the crystallizing dish was most 
convenient for this purpose because of the ease with which 
material could be picked out from it. The large Eremosphaera 
cells were readily found with a hand lens, and then transferred 
by means of a pipette to a watch glass. Here they were washed 
several times in sterilized water, and then examined under the 
microscope, before being placed on the culture medium. 
Various methods of cultivation were tried. The well-known 
solution of Knop was used in strengths from 0.2 per cent. up to 
I per cent., both as a fluid culture and in connection with agar 
agar and gelatin. The gelatin was soon abandoned, however, 
on account of the low temperature at which it liquefied, since 
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