﻿Dodge: Effect of host on Gymnosporangium 523 



not found spores that had more than two cells. Kern (9) states 

 that each cell has two pores near the septum. In the great 

 majority of the spores the upper cell has a pore at the apex, and 

 it is more frequently through this pore (Plate 29, figs. 33-35, 37) 

 that the germ tube appears. The pedicel possesses a character- 

 istic feature noted by Farlow (3) in his discussion of "G. davipes." 

 The "collar," which remains attached to the lower end of the 

 spore after the pedicel has swollen and has more or less dis- 

 appeared through gelatinization, is apparently the upper portion 

 of the stalk cell wall which becomes disorganized for the most 

 part when moistened. The upper end still persists along with the 

 protoplast which is seen as a long thread-like appendage. The 

 stalk cell is originally cylindrical as described by Kern (9), but 

 when moistened it frequently becomes carotiform (FiG. 26), 

 resembling in this condition the pedicel of G. davipes, though the 

 thickening is much less noticeable. The two-celled spores of G- 

 biseptatum resemble in every respect the spores of G. fraternum 

 (Figs. 31, 32)- 



On April 19, 1914, I found at Newfield a large quantity of 

 G. fraternum on seedlings of Chamaecyparis a few inches high as well 

 as on trees of all sizes. In a few cases the same branches bore 

 both G. biseptatum and G. fraternum. The latter also occurred on 

 small trees which were at the same time heavily infected with the 

 witch's-brooms of G. Ellisii. At the place where G. fraternum 

 was the most abundant there was a good growth of Amelanchier 

 and Aronia. The leaf buds of the shrubs had not opened to any 

 great extent, and there were no indications that the sori of the 

 Gymnosporangia had reached sufficient maturity to have swollen 

 and scattered sporidia during any rains that may have occurred 

 pre\dous to this date. The season was somewhat "late." 



Infected seedling cedars were brought in and potted, and root 

 sprouts of Amelanchier, Aronia, and Pyrus were also obtained from 

 this locality and from the grounds of the New York Botanical 

 Garden. It required five or ten days for the leaf buds to open 

 sufficiently for these plants to be used for inoculation purposes; 

 at the end of this time the sori on the cedars had also reached 

 maturity. 



Inoculations were made in the greenhouse, and the usual 



