132 DIFFUSION AND OSMOTIC PRESSURE 



cane-sugar solution, that is, about 111.5 atmospheres. Raci- 

 borski 1 found the maximum concentration for growth of 

 Basidiobolus was that of a 6 per cent, solution of NaCl, or 

 about seventeen atmospheres. Yasuda 2 published an account 

 of some experiments upon infusoria which have a bearing 

 here. He finds that these organisms are able to adjust 

 themselves to solutions of quite high concentration, and 

 that, in general, the limit of their power of adjustment 

 seems to be at about the same osmotic pressure, no matter 

 what salts are used. In other words, the limit to adjust- 

 ment is apparently an osmotic one and depends upon with- 

 drawal of water. 



The experiments of the present author 3 upon the physi- 

 ology of polymorphism in Stigeoclonium need to be con- 

 sidered here. In the stronger solutions (pressure from 

 323.7 cm. to 647.4 cm. Hg.) this alga takes the form of 

 groups of spherical cells with somewhat gelatinous walls. 

 Multiplication takes place rather slowly, cell division occur- 

 ring in all directions and the daughter-cells immediately 

 rounding up so far as they are not hindered by adjacent 

 cells. In weak solutions (pressure below 161.8 cm. Hg.) the 

 behavior is entirely different. The daughter-cells elongate 

 into branching filaments composed of cylindrical cells and 

 having the typical appearance of Stigeoclonium. Growth is 

 much more rapid here than in the strong solutions. If fila- 

 ments are transferred to a strong solution, the cells round 

 up and break apart, thus producing the other form. 



1 M. RACIBOBSKI, " Ueber den Einfluss ausserer Bedingungen auf die Wachs- 

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



2 ATSUSHI YASUDA, " Studien uber die Anpassungsfahigkeit einiger Infusorien 

 an concentrirte Lflsungen," Jour. Coll. Sci. Imp. Univ. Tokyo, Vol. XIII (1900), pp. 

 101-40. Reviewed in Bot. Gaz., Vol. XXX (1900), p. 285. 



3 B. E. LIVINGSTON, (1) " On the Nature of the Stimulus Which Causes the 

 Change of Form in Polymorphic Green Algae," Bot. Gaz., Vol. XXX (1900), pp. 289- 

 317; IDEM, (2) "Further Notes on the Physiology of Polymorphism in Green Algae," 

 ibid., Vol. XXXII (1901), pp. 292-302. Some parts of the discussion here given are 

 quoted from these articles. 



