UPWARD PRESSURE OF THE STIPE 



119 



pound. Doubtless the stouter fruit-bodies of Coprinus sterquilinus 

 are able with the tops of their stipes to exert an upward pressure 

 of at least half a pound. 



Small dung-balls weigh about 1 oz., large ones about 2 oz., and 

 even very large less than 3 oz. The experiment just described, 

 which shows that a fruit-body can exercise an upward push of at 

 least 7 oz., makes it easy for us to 

 understand how it is that a young 

 fruit-body is able to push upwards 

 two or three dung-balls which in 

 dung-ball heaps may oppose its up- 

 ward growth. The pileus of a young 

 fruit-body is conical in form (Fig. 

 69, B), the sohd flesh at its top is 

 borne directly upon the end of the 

 stipe, and its tip is mucilaginous 

 and slippery. In its mechanical 

 quahties it therefore resembles 

 root-cap and is admirably adapted 



Fig. 68. — Co2yriniis sterquilimis. Measurement 

 of tlie lifting power of a developing fruit- 

 body. A large glass crystallising dish a 

 contains sterilised horse-dung balls b in 

 wliicli has grown a mycelium which has 

 given rise to the vertical fruit-body c of 

 which the base of the stipe is firmly seated 

 on the bottom of the dish. About 24 

 hours previously the pileus (c/. Fig. 67) 

 was covered with the glass cap d. The 

 space e between the sides of the pileus 

 and the glass cap was filled with cotton- 

 wool (not here shown). Upon the glass 

 cap now rests a weight of 200 grams 

 made up of (1) the test-tube / and its 

 content of lead shot weighing 150 grams 

 and (2) the brass weight g weigh- 

 ing 50 grams. The test-tube / 

 and the weight g are kept in an 

 approximately vertical position by 

 the loose glass sheath h held 

 by the wooden clamp i. The 

 fruit-body pushed up the weight 

 of 200 grams a distance of 2 mm. 

 in an hour and a half. When the 

 weight was increased to 300 grams, 

 the stipe bent and broke. Reduced 

 to two-thirds the natural size. 



