372 RESEARCHES ON FUNGI 



collapsed bodies of such basidia before the death of the gill as a 

 whole. Further particulars in regard to this matter, however, 

 will be given later on. 



Evolution of Ammonia from Dead Fruit-bodies. I placed three 

 pilei of the Common Mushroom on the bottom of a crystallising 

 dish which was about 8 inches wide, covered the dish with a 

 glass plate, and kept the whole on a laboratory table at ordinary 

 room temperatures. The pilei in the course of a few days died, 

 collapsed, and became subjected to the action of putrefactive 

 bacteria, which reduced them to a pulp and caused an exudation 

 from them of a dark brown fluid. As soon as putrefaction was 

 in full operation, a large amount of free ammonia was emitted. 

 This gas, which rapidly turned red litmus paper blue, could easily 

 be detected by its odour which was very characteristic and pungent, 

 and it gave the usual reactions in chemical tests for ammonia. 

 This experiment has been repeated in successive years, and I now 

 use it to demonstrate to students that free ammonia may be 

 liberated into the atmosphere through the action of putrefactive 

 bacteria. 



General Organisation of the Fruit-body for the Production 

 arid Liberation of Spores. The hymenium or spore-producing 

 layer is situated upon the under side of the pileus. This position 

 is fraught with various advantages. The dominating one is that 

 it favours the escape of the spores, for, when these have been shot 

 a little distance from the basidia which have produced them, they 

 fall into a free space beneath the pileus whence they can be carried 

 away by the wind without meeting with any obstacle. The sub- 

 pilear position of the hymenium also secures the protection of the 

 basidia from falling rain, from too rapid loss of water by trans- 

 piration during dry weather, and from the direct heating effect of 

 the sun's rays. 1 



The hymenium is situated on the surface of several hundreds 

 of lamellae which are packed closely together. Each of these 

 structures is shaped much like the blade of a pen-knife with the 

 cutting edge directed downwards. The production of the lamellae 

 throws the hymenium into a series of folds and therefore serves 



1 Cf. vol. i, 1909, pp. 21-24. 



