120 RESEARCHES ON FUNGI 



to be pushed upwards between obstacles, such as dung-balls, by the 

 pressure exerted by the stipe. As was mentioned at the beginning of 

 this Section, a dung-ball is sometimes broken into two or more pieces 

 by the pileus, if it cannot be pushed to one side. A dung-ball has 

 not sufficient mechanical resistance to withstand either the lifting or 

 the splitting power of the young fruit-bodies. In nature, there- 

 fore, if a fruit-body arises in a dark crevice between dung-balls 

 low down in a dung-ball heap, the fruit-body is able to exert 

 sufficient pressure in its upward growth to enable it with certainty 

 to escape from imprisonment and to reach the free surface of the 

 substratum. Here again, therefore, we have another example of 

 the beautiful manner in which Coprimis sterquilinus is adapted to its 

 environment. 



The stipe-shaft is a hollow cylinder. A transverse section was 

 made through the stipe enclosed by the pileus in the experiment 

 described above, and the area of the solid part was measured. 

 This area was 0-045 square inches. The weight pushed up by the 

 solid part of the stipe was the weight of the pileus plus the 

 weights added artificially. Since the pileus weighed 2 ■ 5 grams, 

 this weight was 204 grams in all. From this it was calculated that 

 the pressure exerted by the solid part of the stipe in pushing up 

 the pileus with its load had been approximately two-thirds of an 

 atmosphere.^ 



^ There are a number of recorded instances in which a heavy stone has been 

 raised by the expansive power of one or more agaricaceous fruit -bodies growing 

 beneath it. Thus M. C. Cooke (A Plain and Easy Account of British Fungi, London, 

 1862, pp. 6-7) tells of " a large kitchen hearthstone which was forced up from its 

 bed by an under-growing fungus and had to be relaid two or three times, until at 

 last it reposed in peace, the old bed having been removed to a depth of six inches 

 and a new foundation laid." Cooke also cites a comparable observation made 

 by Dr. Carpenter : " Some years ago the town of Basingstoke was paved ; and not 

 many months afterwards the pavement was observed to exhibit an unevenness 

 which could not readily be accounted for. In a short time after, the mystery was 

 explained, for some of the heaviest stones were completely lifted out of their beds 

 by the growth of large toadstools beneath them. One of the stones measured 

 twenty-two inches by twenty-one, and weighed eighty-three pounds." ]\Ir. C. V. B. 

 IMarquand of the Kew Herbarium has informed me that, when he was a boy, he 

 observed at Guernsey, in a pavement, a large flagstone which had been raised on 

 one side to a height of two or three inches. On looking beneath the stone, he 

 observed there a group of hard, woody fruit-bodies {1 Lentinus lepideus) which 

 appeared to him to have been the causal agent in raising the stone. While it 



