PANAEOLUS CAMPANULATUS 275 



an area measuring only one two-hundredth part of a square milli- 

 metre. It is to be remarked that the gill, before being removed 

 from the fruit-body, had been shedding spores for about 24 hours, 

 so that it was quite certain that it contained a considerable number 

 of exhausted basidia. . The results of the analysis of the area under 

 study will now be given in detail. 



The area investigated was part of what we have called, in dis- 

 cussing the phenomenon of mottling, a black area, i.e. it contained 

 several almost equal-aged basidia all bearing black spores. These 

 basidia, which were six in number, belong to what we shall hence- 

 forth call the present generation. They are shown in their proper 

 positions relatively to the other hymenial elements in Fig. 94 

 at A. It will be noticed by reference to this Figure that the bodies 

 of these basidia have the maximum diameter and that no two of 

 them are in contact with each other. Basidia of any one generation 

 are always separated by other elements. If they were not, it is easy 

 to see that at maturity, owing to the fact that the perimeter which 

 would include the four spores is always greater than the perimeter 

 of the basidium-body, the spores of any two adjacent basidia would 

 seriously interfere with each other and prevent free development 

 and discharge. The avoidance of this mutual interference by means 

 of suitable spacing is one of the most beautiful points in the organisa- 

 tion of the hymenium. It can be realised best by the study of a 

 large area such as that shown in Fig. 89 (p. 257). The present- 

 generation basidia in the small area under discussion have been set 

 out by themselves in Fig. 94 at C. 



We may now turn our attention to the past generations of basidia, 

 i.e. to those generations which have already shed their spores and 

 the members of which are now in the collapsed condition. These 

 exhausted basidia can be distinguished by their size, somewhat 

 irregular outline, sterigmatic stumps, and by the absence of proto- 

 plasmic contents (Fig. 94, A, a). They are also non-protuberant : 

 if one has just focussed the tops of the bodies of basidia of the 

 present generation, then one has to focus downwards in order to 

 bring the tops of the exhausted basidia into view. The basidia of 

 the past generations all look approximately alike : one cannot 

 distinguish one past generation from another. In Fig. 94 at B all 



