304 BOTANICAL GAZETTE — [NOVEMBER 
before reverting to the palmella form. In my weakest solution 
they often attained a length of twenty-five to thirty cells (but 
the older cells here are destroyed in the act of producing 
zoospores, which will presently be discussed), while in my 
strongest solution the few filaments produced seldom attained a 
length of over two cells. The tips of filaments are quite sharply 
pointed in weak solutions, but blunt in strong ones. 
A maximum pressure beyond which filament growth cannot 
take place lies somewhere between 1928 x 1oand 2892 X_ 
10*. No limit was found beyond which no filaments at all 
could be formed. 
3. Response in reproduction.—The most marked response of this 
form to the change in osmotic pressure conditions is the sudden 
production of enormous numbers of zoospores. In some of my 
cultures almost every original cell has thus emptied out its con 
tents within ten or twelve days of the date of transference. In — 
general, within a fortnight and often within five days these very 
weak solutions become literally swarming with zoospores, and 
their production continues as long as the pressure remains lof: 
Zoospores come both from original spherical or parenchyma-like 
cells and from the older cells of filaments radiating from the 
palmella mass. This method of producing zoospores bee often a 
been resorted to by various writers, and Klebs especially hss : 
found it successful in a great variety of forms. But, as ge 
I know, previous writers have not tried to determine the re 
Nature of this weak solution stimulus. 
As would be expected from the response i 
growth, when zoospores come to rest in these we : 
and begin to enlarge, they do so by elongating into 4 ches. 
which soon divides transversely and later produces eee 
{ figs. 8, 14, 78, 32). Thus the response to low osmotic a 7 
of a zoospore which has come to rest is the same 4° a 
young cell of the palmella form. Zoospores often grow 4 ae 
ends, however, which I have not observed in case of oe thus 
The two cells formed by the first division of the 2008 
sometimes become a base from which reach out two long bs | 
ing filaments (figs. 2, 78). 
n vegetative 
