PSALLIOTA CAMPESTRIS 421 



least resistance of which each nucleus can take advantage during 

 its migration. 



In the Wild Mushroom, where most of the basidia are quadri- 

 sporous, the passage of the four nuclei into the four spores probably 

 takes place in the typical manner described above. In the Culti- 

 vated Mushroom, according to Maire, two nuclei travel up each 

 of the two sterigmata into the two spores. Further investigation 

 is required to determine whether the tip of each of the two sterig- 

 mata contains two centrosomes instead of the normal one, and 

 whether or not, just before the nuclear migrations, there are 

 two fibrillar strands running through each sterigma, each strand 

 connecting a nucleus with the apex of the same spore. 



The future-generations basidia, dd (Fig. 146, p. 416), are 

 distinguished from the present-generation basidia by not bearing 

 sterigmata or spores, and from the coming-generation basidia by 

 their relatively small size and by the fact that they are not yet 

 protuberant. They are usually filled or nearly filled with fine proto- 

 plasm, and their basidium-bodies, which are always shorter than 

 those of the present-generation and coming-generation basidia, 

 are relatively transparent. It is possible that the two nuclei 

 with which each of these basidia is provided at its origin have not 

 as yet fused, but this point awaits decision by means of a direct 

 investigation. The future-generations basidia vary somewhat in 

 size, and one is led to suspect that eventually the larger ones 

 produce spores before the smaller. In the piece of hymenium 

 represented in Fig. 146, the future-generations basidia are more 

 numerous than those of any other class. This is associated with 

 the fact that the hymenium is still young (it is supposed to have 

 been shedding spores for only about 24 hours). The future-genera- 

 tions basidia will develop spores during the next three or four 

 days of the spore-discharge period, at the end of which time they 

 will all have become past-generations basidia. It is probable that 

 the total number of generations of basidia produced on any one 

 small area of the hymenium is at least ten. 



The paraphyses, ee (Fig. 146, p. 416), are numerous small 

 elements which are non-protuberant and largely hidden by the 

 basidia, especially by the swollen ends of the bodies of the 



