504 RESEARCHES ON FUNGI 



first beginning as a tiny rudiment to full size was found to take from 

 15 to 25 minutes : the average time was 20 minutes (Fig. 203, a-d). 

 In the Hymenomycetes, at least in some species, the growth 

 period for the spores is practically identical with that for Puccinia 

 graminis. Thus in Collybia velutipes the period was observed to be 

 about 15 minutes, in Armillaria rnellea 20 minutes, and in Psalliota 

 campestris 40 minutes.^ After attaining full size, a spore ripens : 

 its full allotment of protoplasm passes into it through the sterigma, 

 and changes take place at the base of the hilum which enable dis- 

 charge to be effected. The length of time taken for a full-grown 

 spore to ripen was not measured, but may be of the order of one 

 hour. A spore, as soon as it is ripe, is shot away from its sterigma 

 to a distance of a few tenths c ' a mm.^ 



After spending a considerable amount of time in concentrating 



my attention on individual basidia, I succeeded in observing the 



discharge of a few spores from their sterigmata in detail. In one 



preparation, where a basidium projected into the air, I clearly 



perceived that a tiny drop of water began to be excreted at the 



hilum at the base of one of the spores (Fig. 203, e). The drop 



grew visibly in size, and in from 5 to 10 seconds it became a little 



wider than half the diameter of the spore. Then the spore was 



violently shot away from its sterigma and disappeared from view 



(Figs. 203, / and g, 204, A, 6 and c). The drop disappeared at the 



same time as the spore and was doubtless carried with it, as in the 



Hymenomycetes, for it was not left on the vacant sterigma. The 



sterigma did not immediately collapse but seemed to remain turgid 



(Fig. 204, d). I have very little doubt that this mode of discharge, 



which corresponds to that described by Dietel for other Uredineae 



and to that which I have already described for the Hymenomycetes 



1 These Researches, vol. ii, 1922, p. 54. 



2 The basidia of the grain rusts, Puccinia graminis, P. dispersa, and P. glumarum, 

 represented by Jakob Eriksson in his Fungoid Diseases of Agricultural Plants 

 (London, 1912, Figs. 42, 44, and 47, pp. 69, 74, and 80) are all abnormal in form. 

 They are' shown as chains of cells either breaking up directly into separate cells or 

 as directly constricting off conidia. Sterigmata are absent and the conidia have no 

 hilum. Possibly these abnormal basidia were developed under too moist conditions. 

 Unfortunately, Eriksson's drawings of the basidia of P. graminis and P. glumarmn 

 have been reproduced in von Tuboeufs coloured wall-diagrams, V and VI, designed 

 for the instruction of students. 



