PSALLIOTA CAMPESTRIS 403 



that the spore-discharge period is more than double forty-eight 

 hours, we must conclude that the number 1,800,000,000 was much 

 less than the total number of spores which would have been 

 liberated, had the pileus not been cut off from its stipe but allowed 

 to continue its development to the point of exhaustion in 

 nature. 



The number of spores which a mushroom can produce was 

 found by counting the basidia in the following manner. A gill 

 of a wild mushroom, which had been shedding spores for about 

 two days and one night, was removed from the pileus and treated 

 with chlor-zinc iodine. The reagent killed the hymenial cells, but 

 all those basidia which were developing or were soon to develop 

 spores were stained a decided yellow, owing to the presence in 

 them of accumulated protoplasm containing proteins. The yellow 

 basidia on an area of the hymenium measuring forty-nine ten- 

 thousandths of a square mm. were all sketched on paper with the 

 help of a camera lucida and were found to number 108. By filling 

 up the spaces in the area and thus allowing for the exhausted 

 basidia which had already shed spores during the period of about 

 two days and one night already mentioned, the number of basidia 

 for the area was increased to 164. The increase allowed for four 

 generations of basidia, fourteen to a generation on the area under 

 investigation, the number 14 being the same as that found by 

 actual observation of similar areas of the living hymenium on 

 other gills of the same fruit-body. The number of generations 

 belonging to the past-generation basidia was taken as four, this 

 being the number which could shed their spores successively in 

 36 hours if each generation took about 8 hours and 30 minutes 

 for its full development. 1 If we suppose, therefore, that the total 

 number of basidia on forty-nine ten-thousandths of a square mm. 

 is 164, then on one square mm. there would be 33,265 basidia, and 

 these would produce 133,060 spores. The number of spores pro- 

 duced by a square inch of hymenial surface would be 83,162,500 

 approximately. Now a mushroom about three and three-quarters 

 of an inch in diameter was found to have a hymenial area of 195 

 square inches. Supposing the packing of the basidia per square 

 1 Vide Chapter II. 



