322 RESEARCHES ON FUNGI 



One of the difficulties with which I had to contend in determining 

 the range of Sphaerobolus was in keeping the little guns sufficiently 

 moist after they had been taken from a damp-chamber and had 

 become exposed to the dry air of a large room. In the depth of 

 winter, at Winnipeg, the air in the laboratories and dwelling-rooms 

 becomes extraordinarily dry. To counteract transpiration, there- 

 fore, it was found necessary to moisten the board or dung around 

 each opened fruit-body or to place pieces of wet filter paper, etc., 

 on the substratum so that they just touched the lower part of the 

 outer peridium. 



The experiments now to be described demonstrate not only that 

 the discharge of the Sphaerobolus gun has nothing to do with desic- 

 cation and is favoured by a good supply of water, but also that the 

 elasticity of the cell-walls is a factor in the eversion of the dual 

 inner membrane of the peridium. 



One day at noon, the dual membranes (palisade layer and fibrous 

 layer combined, vide Fig. 161, C, p. 316) of eight fruit-bodies which 

 had opened stellately were removed and, together with the enclosed 

 glebal masses, were submerged beneath the surface of some water 

 contained within a crystallising dish. Thereafter, in the course of 

 a few minutes, in succession, all of the eight membranes suddenly 

 everted and discharged their projectiles ; and some of them everted 

 with such force that the impact of the projectiles as they struck the 

 side of the crystallising dish beneath the water could be heard at 

 a distance of several feet. 



Some dual everting membranes, after removal from stellately 

 opened fruit-bodies, were placed in one or another of the three 

 following reagents : (1) 10 per cent, potassium nitrate, (2) water to 

 which a little 95 per cent, alcohol was added, (3) water to which 

 a little iodine was added. Spontaneous eversion did not take place 

 in any of these liquids. 



In the solution of potassium nitrate the membranes soon con- 

 tracted so that the teeth, instead of remaining spread radially out- 

 wards, curved tangentially inwards, while the main part of the 

 membranes below the teeth became softened. This was doubtless 

 due to exosmosis and consequent reduction of the turgidity of the 

 living cells. The semiglobose main part of the membranes, however, 



