NOTES ON OSMOTIC EXPERIMENTS WITH MARINE 
RopNEY H. TRUE 
During the summer of 1899, when the writer was engaged in 
plant physiological investigations at Woods Hole, he took the oppor- 
tunity to study the osmotic properties of a number of algae from 
both fresh and marine waters. These studies were not complete, 
but since they shed some light on relations which still have much 
physiological interest, the results are here presented. Moreover, 
since that time, through the work of Morse and his associates (15), 
BERKELEY and HartTtEy (1, 2, 3), and others, the recalculations of 
osmotic relationships have resulted in important changes. ‘The 
bearing of the work of physicists on the problems of physiology has 
been pointed out by RENNER (20), who has done much to resolve 
the difficulties involved in the question. The osmotic values here 
dealt with have been calculated according to the newer methods. 
In some cases the values calculated according to PrEFFER’s (18) 
data are added in order to enable the reader to contrast the values 
obtained under the two methods of reckoning. 
Osmotic pressure in Spirogyra cells 
It was desired first to ascertain an approximate measure of the 
osmotic value of the sea water at Woods Hole. For this purpose 
some organism having a lower osmotic pressure than that of the | 
Sea water was sought. Several fresh water algae, Spirogyra elon- 
gata(?), Zygnema (sp.), and Oedogonium (sp.), found growing in a 
small fresh water pond between Woods Hole va Nobska Point, 
were tested. 
Preliminary experiments with the distilled water available 
showed the presence of injurious impurities, probably copper from 
the still. The addition of shredded filter paper to the stock bottle 
was found to remove the pathological symptoms, and the solutions 
* Published by permission of the Secretary of Agriculture. 
71] [Botanical Geli vol. 65 
