GENERAL SUMMARY 465 



asci were all to be discharged in succession as they ripen, none of the 

 spores (we may suppose) would travel upwards more than an inch or 

 two ; but, if the asci ripen one by one and then wait before exploding 

 until some suitable stimulus sets them all off together, then the spores 

 may be carried upwards by the blast of air, which they bring into exis- 

 tence, to a height of 5-7 inches. After being carried upwards into the 

 air, the spores are borne away more or less horizontally by the wind and 

 then dispersed. The nearer the ground, the less wind there is ; and, 

 every extra inch the spores can be raised into the air by discharge from 

 the apothecium, the stronger will be the wind which they will encounter 

 and the greater the chance that they will be dispersed widely and find 

 suitable conditions for propagating the species. 



Our knowledge of the phenomenon of spore-discharge in the Discomy- 

 cetes is still very incomplete. With a view to its extension individual 

 apothecia of a series of typical species should be observed in the field. 

 Such apothecia should be left in situ and not be touched by man ; and, 

 for each apothecium, during the whole period of spore-discharge, a 

 continuous record, not only of the times of spore-discharge, but also of 

 the conditions of spore-discharge (temperature, moisture, wind-move- 

 ments, etc.) sho^^ld be made. 



Chapter II. — In 1890, Zopf observed that the protuberant asci of 

 Ascobolus denudatus and of a species of Saccobolus are heliotropic and 

 bend toward the source of strongest light. 



As a result of a series of his own observations the author has no 

 doubt that the asci of Ciliaria scutellata, Aleuria vesiculosa, Galactinia 

 hadia, Morchella crassipes, and other similar Discomycetes, like those of 

 the Ascoboleae, are heliotropic, and that the response of the asci to the 

 directive stimulus of light serves to explain how it is that the ascospores 

 discharged from the interior of hollow cups, such as those of Aleuria 

 vesiculosa, Galactinia hadia, etc., and from the interior of cavernous 

 depressions at the surface of the caps of Morchellae are shot outwards 

 into the external air without striking opposing chamber walls. 



Richard Falck expressed the view that, when a Morchella or a Gyro- 

 mitra fruit-body is caused to puff by irradiating it with heat from a lamp, 

 air and water-vapour currents are produced in the hymenial chambers 

 and passages and that these currents bear the spores along and thus 

 enable the spores to escape from the fruit-body. The author is unable 

 to accept this theory. 



To explain the phenomenon of puffing in a Morchella or Gyromitra 

 which has been irradiated by heat from a lamp we have only to suppose : 

 (1) that the asci are sensitive to heat and, when ripe, always explode when 

 their temperature is raised above a certain degree, so that puffing may 

 be initiated by warming a fruit-body ; (2) that the asci are curved 

 heliotropically toward the mouths of the hymenial cavities instead of 

 being straight ; and (3) that the air-currents which arise at the moment 



VOL. VI. 2 H 



