138 DIFFUSION AND OSMOTIC PKESSURE 



Beauverie found that fungus hyphae which normally grow 

 upon the surface of the nutrient fluid, and even rise into the 

 air, lose this habit in concentrated solutions, and remain, for 

 the most part, submerged. Growth continues in these cases, 

 but seems not to be as marked as in weak solutions. Of the 

 hyphaa which do rise into the air from the concentrated 

 medium, the cells are much shorter and broader than those 

 which rise from a weak solution. Details are not given in 

 the published account, but apparently we have here a very 

 similar response to the one which was obtained in the case 

 of Stigeoclonium. 



The same author has also experimented upon flowering 

 plants, e. g., Pisum and Phaseolus. Grown in a strong 

 solution, the stems of these plants are short and thick, and 

 the roots show a remarkable development of cork tissue on 

 their surfaces, with a slight development of pith. He also 

 states that, while in weak solutions an upward bending of 

 the roots normally occurs, in strong solutions these grow 

 vertically downward. The upward bending in weak solutions 

 has been ascribed heretofore to aerotropism. Perhaps the 

 extraction of water which occurs in the strong solution 

 changes the irritability of the roots so that they no longer 

 respond normally to lack of oxygen. In the stems of Pisum 

 and Phaseolus is perhaps presented another case of cells 

 failing to elongate in a solution which extracts water. Much 

 more experimentation is needed, however, before we can relate 

 these responses in higher plants with those of algae and fungi. 



b) The influence of external concentration upon repro- 

 duction. Raciborski 1 states that concentrated solutions 

 check the formation of zygospores in Basidiobolus. In 

 concentrated solutions Stigeoclonium 2 failed to produce any 



i M. RACIBORSKI, " Ueber d. Einfluss ausserer Bedingungen auf d. Wachsthums- 

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



2B. 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. 



