﻿536 Dodge: Effect of host on Gymnosporangium 



My experiments of 1914, confirmed by those of 1915, also show 

 that G. fraternum will infect Amelanchier about as readily as it 

 will Aronia, producing on the Amelanchier hypertrophies and 

 aecidia which may have furnished the basis for Peck's Roestelia 

 Ellisii and which is without doubt now widely distributed in 

 exsiccati under the name R. Botryapites. 



Leaving aside the question of the accuracy or thoroughness of 

 my experiments in attempting to infect Aronia with G. biseptatum 

 the other cultures show that the foliicolous form on Chamaecyparis 

 occurring so abundantly at Newfield and Lakehurst, New Jersey, 

 is the Gymnosporangium connected with the well known Roestelia 

 transformans. 



General discussion 

 The color of the gall on Aronia produced by Roestelia trans- 

 formans is commonly described as red or brownish. To quote 

 from Peck (15) : "Subiculum much thickened, produced into tufts 

 of crowded subcylindrical or cornute processes, red or brownish, 

 sometimes transforming an entire leaf." 



I have noted above that the galls in my cultures remain per- 

 fectly green long after the aecidia are mature, and turn brownish 

 only when old or after much exposure to weathering. 



In 1875 Peck (16) described Roestelia Ellisii, collected by 

 Ellis on leaves of Amelanchier at Newfield. Peck's description 

 might well have been drawn from the form which I have obtained 

 on Amelanchier by inoculation with Gymnosporangium fraternum: 

 "Spots yellow, red or brown; subicular projections clustered or 

 scattered, ovate, greenish, or yellowish; peridia cylindrical, single 

 at the apices of projections, the laciniae remaining united at the 

 apex, the cells linear, subflexuous, smooth. . . . This species is 

 related to R. transformans Ellis, from which it differs in its paler, 

 shorter, and differently shaped subicular projections, the smooth 

 cells of the peridia, and the apically united laciniae." I have 

 pointed out that in R. transformans on Aronia the apical peridial 

 cells remain united, falling off together, and that the color 

 of the galls varies with age. Peck could not have known of R. 

 Botryapites or had it in mind when he described R. Ellisii for all 

 subsequent writers have considered them identical on the basis 

 of the "smooth fiexuous cells," and the form of the galls on the 

 host. 



