PSALLIOTA CAMPESTRIS 423 



As the hymenium gets older and as more and more basidia shed 

 their spores and collapse, the paraphyses become larger and larger, 

 and so fill up the gaps between the still living basidia. To these 

 they probably minister by giving mechanical support and moisture, 

 and possibly in other as yet unsuspected ways. 1 



In Fig. 146 (p. 416), a wave of development is passing across 

 the hymenium from the left to the right in the directions shown 

 by the arrows. This wave has already been dealt with, so far 

 as the present-generation basidia are concerned, in the section 

 which treats of the mottling of the gills (cf. Fig. 142, p. 407, which 

 has the same present-generation basidia in its right two-thirds 

 as Fig. 146). But here all the elements of the hymenium are 

 represented, so that it is now possible to explain the nature of 

 the wave in greater detail. The series of elements nos. 1, 2, 3, 

 4, 5, 6, and 7 in Fig. 146 are basidia in successively younger stages 

 of development. No. 1 indicates two basidia with full-sized but 

 unpigmented spores. The spores are supposed to be only one hour 

 old, and therefore to have attained their full size only about twenty 

 minutes ago. No. 2 indicates a basidium which bears spores 

 which have not yet attained full size. These spores are only 

 about thirty minutes old. The basidium no. 3 bears spores which 

 have attained only one-third of their eventual diameter and are 

 only about ten minutes old. The basidium no. 4 bears spores 

 which have just begun their existence and are only about five 

 minutes old. No. 5 points to two basidia which possess fully 

 developed sterigmata but no spores. The basidium no. 6 has 

 sterigmata which are just beginning to develop. The basidium 

 no. 7 is as yet without even a trace of sterigmata. Similar series 

 of basidia can be seen anywhere in the Figure passing from left 

 to right in the direction of the arrows. Nos. 1 to 4 belong to the 

 present-generation basidia of the light area, while nos. 5 to 7 

 belong to the coming generation of the dark area. Spore-discharge 

 is taking place on the left-hand side of the dark area and is 

 proceeding to the right-hand side in the direction of the arrows. 

 The basidia s s discharged their spores about twenty minutes ago 

 and are in the act of collapsing : their sterigmata are sinking 

 1 Cf. Chap. X, pp. 282-283. 



