1900] CHANGE OF FORM IN GREEN ALG 307 
before death ensued. Often they did not die until they had 
actually taken the palmella form. Where a definite response 
was not observed before death, the cultures are recorded in the 
column headed Died. The graphic arrangement of the numbers 
in this table is even more striking than that in table III. The 
: conclusions to be drawn from the above set of results will be 
4 given in the same order as were those derived from the experi- 
tents upon the palmella form. 
\. Nature of the stimulus.—The stimulus with which we have 
to deal is always of an osmotic nature. Indeed, this generaliza- 
tion would have been expected from the nature of the stimulus 
affecting palmelloid cells, and from the data which we are now 
considering the same facts can be cited in its support. 
2. Response in vegetative growth.— Filaments placed in the 
Weakest solution used (pressure 96 V X 107) continued indef- 
mitely to grow without change in form. No going over to 
Palmella was observed until time enough had elapsed for great 
*oncentration of the solution through evaporation. The rule is, 
if filaments are left in a dish without renewal of fluid, they 
change to the other form at the end of a period of thirty to fifty 
ay By this time the culture is often nearly dry. Also, by 
Addition of water from time to time filaments may be kept 
sowing in a dish as long as one chooses. So there is little room 
°F question as to what the nature of the stimulus producing this 
ey response really is. With higher osmotic pressures 
“pas = the alga to continue as filaments rapidly eee: 
ay dication of such an effect being the blunting of the 
: mal cells, A limiting pressure for free filament growth lies 
“ge somewhere in the region between the pressure of 
| 10 ont fo and 482 V x 10+. With a pressure of 964 = 
“id i. out of forty cultures showed good hielo 
lost aly a et thirty days, while many of these oe a. 
ie. of them within that time. Nota _ e wae 
‘typical gi cultures having a pressure of 2892 NX 10% 5 ang 
Only f aments. at the end of such a period, and there 
_* Strwhich showed filaments at all. As in the other form, 
x 
ie 
a 
if 
Ate 
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