296 



RESEARCHES ON FUNGI 



i 1 1 1 



(Fig. 142, B). Had the hymenium of the ridge been bent concavely 

 downwards — as it is in normal fruit-bodies — instead of convexly 

 upwards, the asci would have looked toward the light in the manner 

 shown in Figs. 139 and 140 ; but there is this difference between 

 the arrangement of the asci in the concave and the convex hymenium : 

 in the concave hymenium (Fig. 140) the asci are turned away from 



the centre of the hymenium, whereas in 

 the convex hymenium (Fig. 142) they are 

 turned toward the centre of the hymenium. 

 The arrangement of the asci on the central 

 convex ridge of our abnormally shaped 

 fruit-body allows us to draw the conclusion 

 that the asci in a normal, more or less hemi- 

 spherical fruit-body do not turn away from 

 the centre of the hymenium because they 

 are influenced by the organisation of the 

 fruit-body as a whole but because they are 

 stimulated by light which causes them to 

 curve heliotropically. 



Sufficient evidence has now been brought 

 forward to justify the conclusion that the 

 asci of Aleuria vesiculosa are positively 

 heliotropic. 



The relations of the heliotropic asci with 

 the paraphyses will now be discussed. The 

 asci of Aleuria vesiculosa, when ripe, pro- 

 trude beyond the paraphyses for a distance 

 of not more than 30 [x (Fig. 140). Now 

 the heliotropic curvature of an ascus on the side of a hemispherical 

 fruit-body of A. vesiculosa is not confined as in Ciliaria scutellata, 

 Melastiza miniata, and Cheilymenia vinacea to the very end of 

 the ascus — the part that j^rotrudes beyond the paraphyses — but 

 begins about the middle of the ascus, i.e. deep down in the 

 hymenium, and includes the whole of the spore- bearing portion 

 (Fig. 140). It may therefore be asked : how comes it that 

 the asci, notwithstanding that they are hemmed in by para- 

 physes, are able to bend at so great a depth in the hyme- 



FiG. 142. — Aleuria vesi- 

 culosa. A, vertical 

 section of irregular 

 fruit-body ; arrows 

 indicate general 

 direction of light. B, 

 diagrammatic repre- 

 sentation of the 

 central ridge of A ; 

 the asci are heliotrop- 

 ically directed toward 

 the light. A, 1-3 

 natiH'alsize ; B,mucli 

 enlarged. 



