292 BOTANICAL GAZETTE [NOVEMBER 
chloroplasts often lose much of their bright green color and 
become pale. Palmelloid cells usually produce seven or eight 
zoospores; the number produced by a filament cell depends 
upon its size. The zoospores are ellipsoidal to spherical when 
discharged into the water by the rupture of the parent wall, and 
immediately begin to move about, swimming by means of two 
long cilia (fig. 3). Each contains a pyrenoid, and often several 
smaller granules; the chloroplast can be seen lying against the 
wall opposite the origin of the cilia and extending in its usual 
cup-shaped form somewhat more than half way around the cell. 
The dimensions of motile zoospores are from 3X6 to 6X9#. 
After swimming freely for several hours, the motion of the cilia 
becomes sluggish and finally ceases altogether; the zoospore 
comes to rest and assumes the spherical form. The diameter 's 
now not far from 64. The chloroplast then regains its original 
bright color, the cell enlarges, and, if conditions are favorable, 
may go over imperceptibly into the palmella form, The cell 
thus produced may dividé a number of times, as described above, 
and then produce more zoospores; or it may produce ps 
immediately upon the attainment of its full size, or even earlier) 
or it may become a resting cell and remain quiescent indefi- 
nitely.? However, a zoospore does not usually show this mode 
of growth. It generally elongates as it lies on the ue 
sometimes at the bottom) of the fluid, and becomes 4 cylin = 
with rounded ends. As it grows longer it bends so nag : = 
becomes somewhat crescent-shaped, semicircular, or even horse S 
shoe shaped, and soon divides into two cells by @ — . 
wall near its middle (figs. 8, 32). Thus a filament 1s “— - 
which soon branches. Its cells produce zoospores sooner 2 
later, according to conditions. 
Methods. 
Pure cultures were first obtained by growing in _ 
. : % : : € 
tion in suspended drops; then the material was trans : 
*KLEBs, G.: Loc. cit. tssch de 
on 
PRINGSHEIM, N.: Ueber die Dauerschwarmer des Wassernetzes- M 
Berliner Akad, 1860, 
or 
rred 10 
