296 Pub. Puget Sound Biol. Sta. Vol. 2, No. 51 



changes could be detected, the time for the examination was extended 

 to about one hour. Decided changes in color usually occurred after 

 about 12 hours. Each oospore is covered with a gelatinous substance 

 which probably accounts for the long period of time required before any 

 definite changes resulted. In no case did a change in color take place in 

 all oospores. 



Eighty per cent of the oospores in seawater having pH values of 6.6 

 and 6.8 changed from red to darker red or purple. No change of color 

 occurred in oospores which were in seawater having pH values between 

 6.8 and 8.2. This indicates that substances potentially acid or alkaline 

 do not permeate the jjlasma membrane in sufficient quantities to change 

 the color produced by staining the oospores with neutral red. Oospores 

 in seawater having pH values below 7.6 were not killed but were in- 

 hibited when the temperature was below 24<°C. This was shown by the 

 fact that when the pH values were allowed to rise, germination and some 

 growth took place. When the temperature of the water was above 

 24- °C the oospores were killed in 3 to 24 hours, depending upon the 

 height of the temperature. Better germination occurs in seawater hav- 

 ing pH values between 7.i and 8.4. The maximum germination is at 

 about 8.0 or 8.2 and gradually decreases on either side. This is in 

 accord with the observations that the plasma membrane was not per- 

 meated by OH or H ions in any considerable quantity in these pH 

 values as is manifest by no change in color. In seawater having pH 

 values of 8.4, 8.6 and 8.8 about 70 per cent of the oospores changed 

 from red to yellow. Usually there was a considerable space between 

 the cell wall and the protoplast. The OH ion had probably produced a 

 sufficient disturbance of the colloidal equilibrium of the plasma mem- 

 brane to bring about plasmolysis. Harvey (1911) reports injurv to be 

 possible when the concentration of the base Avas 0.025N. 



Plate 51 shows a graphic representation of the germination during 

 the first 7 days at different temperatures and the various pH values 

 of the seawater. 



Growth of sporelings 



Oospores were germinated in the usual manner and the sporelings 

 were grown for four weeks. The same conditions and manner of treat- 

 ment were continued that Avere used in the study of the per cent of 

 germination of oospores. The percentage of living sporelings is based 

 on the number of oosjoores that had germinated by the seventh day. 

 Table 3 shows the percentage of living sporelings at the end of foui 

 weeks together with the pH values of the water and the variations in the 



