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196 MISSOURI BOTANICAL GARDEN. 
exclusively bright green cells, scarcely colored by iodine. 
Those left in the dark had increased little or none, were pale 
green and turned dark brown when treated with iodine. The 
first series of CO2 cultures nearly all died on account of the 
strong concentration of the gas used. A second experiment 
with a weaker concentration of COs, after five days, showed 
chiefly ccenobia with spherical cells which colored intense 
brown with iodine. In general, the species C. microporum 
was less resistant and more likely to perish. It was also more 
apt to form single free cells and less so to form ccenobia than 
in the case of Celastrum reticulatum. 
Among my cultures was a flask containing, among other 
things, Celastrum microporum in Knop’s solution, which 
had been standing quietly on a laboratory table for six 
months. On examination it was found to contain many 
cenobia of eight, sixteen, and some of thirty-two cells; some 
of these were beginning to form daughter-cells, or young 
ceenobia. No such large colonies were to be found when the 
original material was taken from the pond in September. 
Although the culture fluid was shallow in the flask, about 
1 em. deep, and the flask plugged only with cotton, the 
conditions were essentially those of stagnant water, and agree 
closely with those employed by Senn (’99) in some of his 
work, though it would require duplicates and extensions to 
justify any final conclusions. 
Some Cladophora placed in a glass jar with a loose glass lid 
and nearly filled with tap water (stagnant condition) showed 
a much more branched condition after a number of weeks 
than the original specimen taken from flowing water, or any 
of the specimens found in free open water, although the water, | 
light and other conditions, aside from aération, were the same. 
The new cells, moreover, were shorter and thicker than in the 
older parts of the original specimen, and the cells had broad, 
thickened, or inflated ends, that showed a branched appear- 
ance or an abnormal tendency toward branching. In the 
older cells the length is usually ten or more times the diam- 
eter; but in these newer cells, and especially the end ones, the 
length is scarcely three or four times the diameter. 
