464 RESEARCHES ON FUNGI 



its contents, reduces its volume to about one-half. The half of the 

 contents of the ascus which is discharged is the upper half which includes 

 the eight spores and a mass of cell-sap. 



The ascus, as a gun, is a squirt from which a jet of watery fluid con- 

 taining eight spores is ejected by the pressure of a contracting elastic 

 cell- wall. The wall contracts more per unit of distance in the circum- 

 ferential direction than in the longitudinal direction. 



Radial-longitudinal sections through a cup and surface views of the 

 hymenium, (1) before puffing has taken place and (2) immediately after 

 puffing has taken place, have been illustrated with a view to showing the 

 exact positions of the asci, the opercula of the asci, the hinges of the 

 opercula, the long axes of the spores, and the paraphyses, relatively to 

 the position of the mouth of the cup as a whole. 



Correlated with the conical form of the cavity of the apothecium of 

 Sarcoscypha protracta and making for efficiency in the production and 

 liberation of spores by the hymenium are : (1) the oblique upward- 

 looking openings of the asci formed at the moment of spore-discharge ; 



(2) the obliquely upward inclination of the spores in each ascus ; and 



(3) the relatively distant separation of adjacent asci by paraphyses. 

 The paraphyses form at least one-half of the hymenial substance. 



They assist the discharge of the spores : (1) by holding the asci fixed in 

 their positions whilst the asci are shooting away their spores obliquely 

 through their apices ; and (2) by keeping adjacent asci sufficiently far 

 apart, thereby preventing the spores of one ascus from hitting the pro- 

 truding end of another ascus during spore-discharge. 



It is probable that, in Sarcoscypha protracta, the mouth of an ascus 

 comes to look upwards toward the mouth of the apothecium as a result 

 of the end of the ascus making a heliotropic curvature. 



By means of an experiment with a test-tube provided with a lateral 

 opening, it has been proved that, when an apothecium pufifs, it produces 

 a blast of air. The blast of air is caused by tens of thousands of spores 

 and sap-drops, which have been shot in the same general direction, 

 striking the air and setting it in motion. 



The significance of the blast of air in respect to the dispersal of the 

 spores has been discussed. If the asci of a fruit-body of Sarcoscypha 

 protracta were to explode one after another as they ripen, it is probable that 

 the eight spores of each ascus would not be shot up into the air more than 

 3-4 cm., and no appreciable blast of air could come into existence to 

 raise them still further. On the other hand, when a hundred thousand 

 asci explode together, i.e. when puffing takes place, the bombardment 

 of the air by the spores and sap-drops collectively is sufficient to create 

 a blast of air which can carry the spores away with it for several inches 

 after they have lost the velocity given to them by the ascus-guns. Under 

 natural conditions in a Poplar wood, the stipe of the fruit-body is nega- 

 tively geotropic and the apothecium looks upward to the sky. If the 



