PUCCINIA GRAMINIS 



505 



Fig. 204. — Comparison of spore-discharge in the Uredineae and the Hymenomycetes. 

 A, a germinated teleutospore of Puccinia graminis (from Avena sativa) bearing 

 two basidia, one with four ripe spores and the other with spore-discharge going 

 on. At a, a spore as it appears about ten seconds before its discharge. At b, a 

 spore at the instant before spore -discharge is effected : a drop of water has been 

 excreted at the hihim and has attained full size. At c, a spore being shot away : 

 it carries the drop with it. At d, a vacant sterigma which has not collapsed 

 although its spore has been discharged some minutes previously. B, a trans- 

 verse section through the hymenium of Psalliota campestris (wild form), showing 

 a basidium with four ripe spores and another basidium with spore-discharge 

 going on. The spores a^, b^, and c^ correspond respectively to a, b, and c in A. 

 In both Puccinia graminis and Psalliota campestris a drop of water is excreted 

 from the hilum of each spore just before discharge. The elements represented in 

 the hymenium of Psalliota campestris may be classified as follows : present- 

 generation basidia, 3 and 11 ; past-generation basidia, 5 (now collapsed and 

 drawn down); coming-generation basidia, 7 and 15 (about to develop spores); 

 future-generations basidia, 1, 6, 9, 13, and 17 ; paraphyses, 2, 4, 8, 10, 12, 14, 

 and 16. Magnification, the same for both A and B, 880. 



generally, is normal for Puccinia graminis. In order that the 

 striking resemblance of the modes of spore-discharge in the Uredi- 

 neae and the Hymenomycetes may be clearly perceived, I have 



