a) CHANGE OF FORM IN GREEN ALGE 305 
In solutions of greater pressure zoospores are produced more 
and more tardily and in fewer and fewer numbers. The limit to the 
healthy production of zoospores lies at a pressure of about 964 
VX 10%. Their production in a higher pressure is exceptional and 
| have never seen them produced at all in my strongest solution. 
With a pressure of 964.V x 10% all zoospores germinate very 
Soon in the manner already described ; some of them go directly 
into the palmella form while most of them germinate to produce 
flaments of two to five cells, and then these pass into the pal- 
_mella condition by rounding and breaking up (figs. 17, 79): 
Thus it often ¢omes about that cultures with this pressure 
show both forms growing together, short young filaments and 
free round cells as well as parenchyma-like masses. With 
Pressures above the observed limit the spores, when they are 
produced, usually grow directly into the palmella form, and 
: then continue to grow slowly, or go into the resting stage. I 
have Ziven little attention to the fate of these resting spores. 
They retain their green color and remain indefinitely at the 
bottom of the culture dish. Klebs has described these and 
a that they may be made to germinate after complete 
drying out. 
B. RESPONSES OF THE FILAMENTOUS FORM. 
: Experimental data from 169 transfers of filaments into the 
: Solutions are presented in table IV, which is constructed 
Mater} a plan as table III. Whether or not the original 
oa changed into the palmella form is shown in the third, 
a ie columns. Cultures in which all or nearly all 
VS are r oe * SS alae the other form within a period of thirty 
Dut not eae in the third column; those in which some, 
» Went over, and long filaments persisted after twenty 
are indicated in the fourth column. The fifth 
© Fesults 
T none aS to the production of zoospores, whether many, few, 
/ © tabulated under those respective heads. Where 
