238 RESEARCHES OX FlXGl 



bursting stage of development, and that the rubbing or shaking 

 simply causes the premature bursting of a few such asci owing to 

 their equilibrium having been mechanically disturbed. According 

 to this theory, the discharge of the asci may be likened to the 

 premature bursting of the capsules of Impatiens, which one may 

 bring about by slight alternate compression and relaxation with the 

 fingers. However, it seems to me not unthinkable that the rubbing, 

 shaking, or moving of a fruit-body may serve to stimulate the proto- 

 plasm in the asci in some way so that it reacts in such a manner as 

 to cause the asci to explode. 



I have tried the effect of various chemical substances upon the 

 discharge of ripe asci lying in water, and I have been unable to 

 confirm De Bary's statement that bursting of the asci can be brought 

 about by agents Avhich withdraw water from them. Sections through 

 the ripe hymenium of Peziza repanda were cut and mounted in 

 water on microscope slides in the usual manner. In order to test its 

 effect upon the asci, a solution of a salt or other substance was then 

 run under the cover-glass gradually. It was found that strong 

 solutions of glycerine, sodium chloride, potassium nitrate, and grape 

 sugar did not cause explosions to occur. The sodium chloride, 

 potassium nitrate, and grape sugar led to considerable contraction 

 in the volume of the asci, so that it is evident that mere withdrawal 

 of water from asci is not sufiicient to cause them to explode. On 

 the other hand, solutions of iodine, mercuric chloride, silver nitrate, 

 copper sulphate, sulphuric acid, acetic acid, and alcohol gave rise to 

 very marked pufiing. A very active discharge of spores took place 

 as soon as the asci came well into contact with these substances, in 

 a number of instances practically all the living asci discharged their 

 spores, and a heavy spore-deposit collected a short distance in front 

 of the ascus mouths. The seven substances last named are all 

 poisonous, whereas the four which do not cause pufiing are non- 

 poisonous. I was therefore tempted to draw the conclusion that 

 poisonous substances cause ])ufiing, whereas non-poisonous ones do 

 not. However, further experiment showed that this rule docs not 

 hold universally. Strong sodium hydrate poisons the asci without 

 causing them to explode. When a solution of this substance was 



