Igor] PHYSIOLOGY OF POLYMORPHISM IN ALGAE 295 
III, which shows the maximum limit for zoospore production in 
each case. It is to be compared with Table V of the former 
article,? from which the figures for mineral solutions have been 
taken. The figures have been altered to round numbers to avoid 
confusion. 
TABLE Ili. 
MAXIMUM LIMITS FOR ZOOSPORE PRODUCTION. 
Sotutions oF NoN-ELEC- 
3 TROLYTES 
ae Mineral 
Original Form Soludions 
Lactose Cane Sugar 
2n in 6 7" 
Panella onion 5008s or 4 a = 
. nt 
Filamentous ....... Eu mas ee. 
Io Io Io 
The filamentous form responds in exactly the same manner 
whether the solution is of electrolyte or non-electrolyte. But 
to bring about an inhibition of zoospore production in the pal- 
mella form requires a much higher osmotic pressure when this 
is produced by non-electrolytes than in the other case. Also 
the two sugars used differ in that the limit for cane sugar is much 
higher than for lactose. Why is this? The volume of the cells 
in the culture is so small, as compared with that of the surround- 
ing fluid, that the difference just spoken of cannot be explained 
by the supposition that the carbohydrate is absorbed and thus 
the concentration of the medium lowered. The amount of 
absorption possible would be entirely inadequate to alter the 
concentration to any appreciable degree. It seems more prob- 
able that by absorption of sugar the concentration of the cell sap 
is increased, thus decreasing the difference between the osmotic 
conditions within and without the plant, and so weakening the 
Stimulus. This would occur if the carbohydrate molecules were 
to penetrate the cells (7. ¢., be absorbed) more rapidly than the 
ions of an electrolyte. It is possible that cane sugar is absorbed 
* Loc cit., p. 313. 
