FURTHER NOTES ON THE PHYSIOLOGY OF POLY- 
MORPHISM IN GREEN ALGAE. 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY. 
BuRTON EDWARD LIVINGSTON., 
Since the publication of the previous article on this subject* 
several additional lines of experimentation have been completed. 
The results of these will be given in the present paper. They 
corroborate the conclusions already expréssed, and also throw 
some further light upon the interesting response with which we 
are dealing. 
I. PHYSIOLOGICAL EXPERIMENTS. 
The experiments here recorded were all performed upon the 
organism used in the previous work, that is, Stigeoclonium tenue 
(?), and the same methods were employed as far as the culture 
media would allow. The cultures may be classified according 
to the media used into the following groups: (1) sugar -solu- 
tions, (2) solutions containing both sugar and mineral salts, (3) 
porous plate cultures, (4) gelatine cultures, (5) cultures in dark- 
ness, (6) evaporation cultures. These categories will be consid- 
ered in order. 
I. SUGAR SOLUTIONS. 
The work already published shows clearly that for changes 
in concentration of Knop’s solution the factor controlling the 
response of the alga is the osmotic pressure. Whether this acts 
upon the organism merely through a change in the relation of 
water to the cell, or in some more complex way, could not be 
decided as long as the pressure was always produced by mineral 
salts. Thus the next step to be taken was to determine the effect 
upon the plant of a solution of non-electrolytes. To this end some 
*LIviNnGston, B. E.: On the nature of the stimulus which causes the change of 
form in polymorphic green algae. Bor. Gaz. 30: 289. 1900. 
292 [OCTOBER 
