52 



HYMXnsl'nKAXCir.M CLAYAKI KI-OUME 



sterigmata, much in the same way in which the basidiospores 

 are thrown off in the Agaricini 1 . Tiny accumulate in large 

 numbers on the outside of the mucilaginous mass, and present 

 the appearance of a golden-yellow powder. The mycelium of 

 the fungus is perennial in the Juniper, spreading from branch 

 to branch and producing a fresh crop of teleutospores each spring. 

 If one of the basidiospores is blown by the wind or carried 

 by insects to a moist leaf or young fruit or stem of Hawthorn, 

 it germinates and holes through the cuticle in the ordinary 

 way, and tonus there a limited patch of mycelium. It is said 

 that the infection has been known to be conveyed for half 



Fig. 31. Gymnosporangium clavariaeforme. -Ecidia on leaf, fruit, and branch 

 of Hawthorn (reduced) ; a, peridium, x 16. The fruit and gall on branch 

 are shown as they appear when the peridia are old, and the mass looks 

 somewhat like a honeycomb. 



a mile. This mycelium produces the aecidium-stage, which is 

 not usually seen until the end of June, in about 18 — 20 days. 

 The secidia are not of the ordinary cup-like shape, but of the 

 form called Rcestelia : they are cylindrical, brown at the base 

 and ochreous above where the peridium is torn into numerous 

 slender filaments (Fig. 31). On the leaves they appear in 

 roundish patches a few mm. in diameter, but on the twigs 

 they form large spongy masses and the fruits are often so 

 covered with them as to look like a cluster of little spikes. 



1 I am indebted to Professor Buller for calling my attention to this fact. 



