PUFFING IN THE DISCO]\IYCETES 



243 



direction in which one might expect the asci to shoot their spores, 

 and in B the direction in which the asci actually shoot their spores. 

 How comes it that the asci do not discharge their spores in the direc- 



FiG. 118. — Sarcoscypha protmctn. Two diagrammatic drawings of a vertical section 

 through a cup, 8 mm. deep, sliowing tlie average slof)e of the liymenium and the 

 direction of tlie long axes of tlie asci. Tiie angle of aperture of the cup is .50". 

 The arrows indicate trajectories of tlie spores shot out by single asci. In .\ the 

 arrows show the direction in which twenty sets of spores would be shot, if they 

 were discharged from the ends of the asci, in the direction in which the asci 

 point, in still air : the asci in the lower two-thirds of the cup would shoot their 

 spores against the opposite walls of the cup ; and the spores which escaped 

 from the cup, as shown by the arrows, would travel obliquely and not vertically 

 upwards. In B the arrows show the general direction in which twenty sets of 

 spores are actually shot. Owing to each ascus having its operculum on the 

 upward-looking side of its end, all the spores escape from the cup and are shot 

 vertically upwards. Magnificatiou, U times the natural size. 



tion in which their ends point 1 The answer must be sought for in 

 a minute study of the individual ascus. 



The Ascus as an Explosive Mechanism. — The hymenium of 

 Sarcoscypha protracta, like that of other Discomycetes, consists of 

 sterile paraphyses and of asci, each ascus containing eight ascospores. 



