INFLUENCE OF THE MEDIUM 137 



one just stated. I have placed filaments in a solution where 

 they were completely plasmolyzed and killed, without any 

 change in form. In solutions a little less concentrated they 

 are not plasmolyzed, but round up rapidly and soon die, 

 often in the palmella condition. With a still lower pressure 

 the filament cells round up more slowly and live. Another 

 fact suggesting this idea is that floating filaments can resist 

 a stronger solution, and can resist it longer, than sunken 

 ones. The former are to some extent in contact with the 

 air, and thus present less surface than the latter to the liquid. 

 Still another observation bearing upon this hypothesis of 

 partial plasmolysis is that cylindrical cells are the only ones 

 which are able to change their form after they have become 

 mature. A spherical cell must remain so till it divides, even 

 if it be in a solution of very low pressure. 



Raciborski 1 made what must be regarded as essentially 

 the same observation as the one just discussed upon Basi- 

 diobolus, concerning the rounding up of cells and the change 

 in direction of cross walls. He states that in strong solutions 

 the cells became rounded and separated from one another, 

 and that walls formed in all directions. Although he paid 

 little attention to osmotic phenomena, yet it can hardly be 

 doubted that Basidiobolus ranarum behaves in much the 

 same way as does Stigeoclonium. 



In a recent paper Beauverie 2 has described some interest- 

 ing effects of the osmotic concentration of the medium upon 

 fungi and higher plants. The concentration of his nutrient 

 fluids was raised by the addition of NaCl a very question- 

 able method, especially in view of the proof brought forward 

 by True 3 that this salt sometimes has a poisonous action. 



1 M. RACIBOESKI, " Ueber d. Einfluss ausserer Bedingungen auf d. Wachsthums- 

 weise des Basidiobolus ranarum," Flora, Vol. LXXXII (1896), pp. 107-32. 



2 J. BEAUVERIE, "Influence de la pression osmotique du milieu sur la forme et la 

 structure des vegetaux," Compt. rend., Vol. CXXXII (1901), pp. 226-29. 



3R. H. TRUE, "The Physiological Action of Certain Plasmolyzing Agents," Bot. 

 Gaz., Vol. XXVI (1898), pp. 407-16. 



