362 RESEARCHES ON FUNGI 



more or less horizontally extended ; and in this state, as is shown 

 by a study of successive spore-deposits, they liberate immense 

 numbers of their very minute spores. In dry weather, however, their 

 edges curl downwards and inwards to such a degree that the gills 

 become almost entirely covered up (Fig. 162). This covermg of 

 the hymenial surface of the pileus also occurs in Schizophyllum 

 commune, Trogia crispa, and some other small lignicolous fungi. 

 Whether or not it has any ecological significance in so far as pro- 

 tection of the hj^menium from mechanical injuries is concerned, is 

 uncertain. It may be that the rollmg up of the fruit-bodies in 

 dry weather, like the rolling up of the leaves of certain Ericaceae 

 and Gramineae under similar conditions, is significant only in so 

 far as it is a means of diminishing the surface exposed and thus a 

 means of bringing about reduced transpiration. 



When the upper surface of the pileus of a dried fruit-body is 

 moistened either naturally by rain-drops or artificially with wet 

 cotton wool, w^ater is quickly absorbed through the squamulose 

 cuticle and, in the course of about an hour, the pileus uncurls and 

 becomes fully extended. In one experiment, made with material that 

 had been kept dry for a few weeks, spore-discharge began to take 

 place within 2 • 5 hours of the time when the pilei were first wetted. 



Dried fruit-bodies of Panus stypticus can retain their vitality 

 for several months. Some fruit-bodies were kept dry in the labora- 

 tory from November 11 until May 10, i.e. for a period of six months. 

 At the end of this time they were allowed to absorb water, where- 

 upon they quickly revived and soon began to shed spores. The 

 white spore-deposits formed beneath the pilei were very copious 

 and the spores, upon being placed in nutrient agar, soon germinated. 

 This confirms a similar experiment made by Miss Johnson.^ 



Some fruit-bodies, which had been gathered in the open and left 

 to dry, after being revived with water in the laboratory, shed spores 

 for a period of 10 days. Doubtless, in nature, the spore-discharge 

 period extends over at least two weeks. In the open the discharge 

 of spores must sometimes be temporarily interrupted by drought, 

 only to be resumed when wet weather supervenes. 



The fruit-bodies of Panus stypticus can successfully withstand 

 ^ E, M. Johnson, loc. ciL, p. 351. 



