238 



OTHER FORMS OF THE RUSTS 



diniospores in the spring, thus, the aecial, teHal and basidial 

 stages are eHminated. In the apple rust, the uredinal stage is 

 missing. This disease produces on the leaves of various members 

 of the apple family, yellow patches in which are formed tube-like 

 cluster cups (Fig. 162, A). The aeciospores are only capable of 

 infesting the juniper, in the branches of which they produce 

 gall-like swellings (Fig. 162, B) known as cedar apples and also 



Fig. 162. A rust, Gymnosporangium, that infests the juniper and mem- 

 bers of the apple family: A, cluster cups on leaf of thorn apple. B, telio- 

 spore stage on red cedar, juniper. 



bushy outgrowths known as witches' brooms. In the spring, 

 tubular masses of hyphae bearing numerous teliospores radiate 

 out from these galls and in the early spring rains these strands 

 swell up, forming conspicuous yellow, jelly-like masses. The 

 basidiospores are developed in the jelly and infest the leaves 

 of the apple, thorn, shadbush, etc. In some of the genera of 

 rusts all the stages appear upon the same plant as in the May 

 apple and jack-in-the-pulpit. In the early spring the stems and 

 leaves may often be seen infected with the yellow cluster cups 

 which are followed later by the dark-colored teliospores. In 

 other cases, teliospores only are produced, as in the hollyhock, 

 and this was doubtless the original form of the spore. Varia- 

 tions in the character of the spore resulted owing to the stimuli 



