COPRINUS AND NON-COPRINUS TYPES 67 



195 square inches in the Mushroom and about 616 square inches in 

 the Coprinus ; and that (2) the pileus-flesh of the Mushroom was 

 about eight times the volume of that of the Coprinus. 



Let A = area of hymenium and V = volume of pileus-flesh. 

 Then 



A of the Mushroom : A of the Coprinus : : 1 : 3, 

 and V of the Mushroom : V of the Coprinus : : 8 : 1 . 



Therefore :^, the ratio of the hy menial area to the volume of the 



pileus-flesh, is 24 times greater in the Coprinus than in the Mush- 

 room. In other words, for every unit of volume of pileus-flesh the 

 Coprinus produces 24 times the area of hymenial surface produced 

 by the Mushroom, or for every unit of area of hymenial surface 

 the Mushroom develops 24 times the volume of pileus-flesh developed 

 by the Coprinus. This well illustrates the extraordinary economy 

 in pileus-flesh effected in a large fruit-body of the Coprinus Type 

 as compared with a large fruit-body of the Non-Coprinus Type. 

 The small amount of flesh in large Coprinus fruit-bodies is a funda- 

 mental characteristic and is correlated with the fact that the gills 

 become hghter in weight as the pileus opens out owing to their 

 destruction by autodigestion.^ 



The advantage which a large Coprinus comatus fruit-body has 

 over a large Psalliota campestris fruit-body in its ratio of hymenial 

 area to volume of pileus-flesh is to a large extent counterbalanced 

 by the disadvantage that, per unit of area of the hymenium, the 

 Coprinus produces a much smaller number of spores than the 

 Mushroom. In other words : in the Mushroom, while a relatively 

 large amount of pileus-flesh is developed for each unit of area of 

 hymenium, each unit of area of the hymenium (owing to its pro- 

 ducing many successive generations of basidia and owing to the 

 small size of its hymenial elements and spores) develops a relatively 

 very large number of spores, i.e. several times as many as there are 

 on each unit of area in the Coprinus. If, therefore, the number of 

 spores produced per unit volume of fruit-body material be taken 

 as a criterion of fruit-body efficiency, then a large Coprinus comatus 

 fruit-body and a large Psalliota campestris fruit-body may well be 

 ^ Cf. these Researches, vol. i, 1909, p. 214. 



