Dodge : 



The Genus Gymnosporangium 



189 



With the gradual increase in size of the cells as we pass from 

 the margin we find a corresponding enlargement of the nuclei, 

 although there is considerable variation in this respect. At the 

 margin the nuclei are small and spherical or elliptical in outline. 

 Pear-shaped nuclei or nuclei with beak-like extensions are often, 

 found in the older cells. The terminal cells do not necessarily 

 form a perfectly even layer. Some cells extend much beyond 

 others. This is due to the inequality in the rate of growth, and 

 perhaps to the fact that some of the cork cells give way more easily. 

 The gall is often irregular in outline. 



Having shown that the leaf forms of Gymnosporangium on 

 Chamaecy parts, and the two cedar apple rusts on the red cedar 

 develop their teleutospores from subterminal basal cells, we may 

 next consider G. clavariae forme which ordinarily inhabits the 

 stem of the common juniper. 



Gymnosporangium clavariaeforme 



Artificially infected junipers furnished the basis for the study 

 of G. clavariae for me. Sori in several stages of development 

 were found January 17 in the stems of small plants ten days after 

 they had been taken from the cold frame. The cork covering 

 these young stems was not thick enough to cause any serious 

 trouble in fixing or sectioning. Sappin-Trouffy and Blackman 

 studied the origin of the teleutospore in this species and found 

 as previously noted that the terminal cells of the hyphal mass give 

 rise directly to buds from which spores will develop. A brief 

 examination of my material was sufficient to show that such is 

 not the case. The method of origin here is just the same as it 

 is in the species which I have discussed above. The sori on the 

 stem present very much the same picture as do those of G. glo- 

 bosum and it is unnecessary to go into details further than refer 

 to figures 6 and 7 in plate 10 which show small portions of a young 

 sorus, one near the margin, the other toward the center. In the 

 first figure we see that the hyphae have pushed up against the 

 cork layers, the end cells have become flattened and rectangular 

 in shape. There is then the same characteristic elongation and 

 degeneration of these terminal cells, and buds grow out from the 



