CHAPTER VIII 



THE SPORE-FALL PERIOD 



The spores of a hymenomycetous fruit-body, under favourable 

 conditions, are liberated continuously at a fairly constant rate. 

 They are never all discharged simultaneously or set free in inter- 

 mittent showers. The falling spores may be compared to raindrops 

 steadily falling from the clouds on a wet day. The process of 

 spore-discharge often requires a considerable period of time. This 

 may be conveniently called the spore-fall 'period. 



In any given fruit-body, the spore-fall period varies in length 

 according to the rate of development of the spores. This depends 

 on internal organisation and also upon external conditions, more 

 particularly of temperature. For many corky or leathery fruit- 

 bodies, such as those of Lenzites, Polystictus, Stereum, &c, 

 which readily become dried up in a dry atmosphere and 

 quickly absorb free water through the upper surfaces of their 

 pilei, rainfall and dew formation are distinctly favourable to 

 the discharge of spores, whilst drought must often temporarily 

 interrupt it. 



It has already been reeorded 1 that a large specimen of Poly- 

 porus squamosus, growing on a log, was observed to shed its spores 

 continuously for sixteen days. Reasons were also given for sup- 

 posing that in this case the spore-fall period must have extended 

 over at least three weeks. 



The length of the spore-fall period was determined for a number 

 of xerophytic fruit-bodies by means of the beam-of-light method. 

 The fruit-bodies which had been detached from the substrata and 

 allowed to dry up were revived in a damp-chamber, suspended 

 in beakers, and examined usually several times a day with a beam 

 from an arc-light. The beakers were kept in a well-heated labora- 



1 Chap. VI. 



