HISTORY OF PILOBOLUS 27 



When chloroform or ether vapour is introduced very slowly 

 into the air surrounding the sporangiophores and the first amounts 

 are small enough, water excretion ceases, but with larger doses 

 water excretion is increased. Sufficient vapour of alcohol, hydro- 

 chloric acid, ammonia, or sulphuretted hydrogen also increases the 

 energy of excretion. An increased excretion can be obtained if 

 one sets the fungus tuft on a solution of any of these substances or 

 caffeine. When some of the sporangiophores of Pilobolus longipes 

 were exposed to the vapour of alcohol for five minutes, the energy 

 of water excretion, which during the night had been 4 • 1 , was raised 

 to 250 ; and when a tuft of sporangiophores of P. Kleinii was set 

 on a 0-5 per cent, solution of caffeine for two minutes, the energy 

 of excretion, which during the night had been 2, was raised to 42. 

 The increase of water excretion caused by anaesthetics and other 

 poisonous substances is accompanied by a decrease in the cell- 

 turgor. The drops excreted under the action of alcohol vapour 

 contained 1 • 9 per cent, of dissolved substances instead of the usual 

 0-6 per cent.^ 



Diffused fight has no influence on the excretion of water, but 

 direct sunlight causes its cessation. ^ 



On the basis of his experimental results Lepeschkin discussed 

 various theories devised to explain how it is that a cell, such as the 

 sporangiophore of Pilobolus, is able to absorb water in one part and 

 excrete water in another part. Since the excretion of water in the 

 form of a drop at one spot in the sporangiophore is continuous and 

 steady, he rejected the hypothesis of Godlewski which postulates 

 alternating periods of greater and less osmotic pressure in the cell 

 and corresponding periods of non-excretion and excretion due to 

 the expansion and contraction of the protoplasm .^ Having observed 

 that a sporangiophore which has been washed by dipping in water 

 and has been again brought into moist air continues to excrete 

 water in the form of drops,* he also rejected the theory of Wilson 



1 W. W. Lepeschkin, he. ciL, pp. 416-il8, 434. 



2 Ibid., p. 418. 3 /ij^^ p_ 419, 



* Wilson (loc. cit.) washed sporangiophores in water with a brush, then set them 

 in moist air, and thereafter observed that, often, the sporangiophores did not excrete 

 any more drops. Hence he concluded, according to Lepeschkin erroneously, that 

 washed sporangiophores do not excrete water. Lepeschkin states that washing 



