﻿530 Dodge: Effect of host on Gymnosporangium 



Myricacaroliniana. Spermogonia appeared in seven days. Aecidia 

 were ripe within four weeks. Four plants of Comptonia and ten 

 of Aronia were inoculated at the same time in the same chamber, 

 with negative results. 



With the alternate hosts of G. Ellisii and Roestelia transformans 

 known, only one phase of the question has been solved. 



It is a common practice in establishing a connection between 

 two phases of a heteroecious rust to rest content when the rust 

 has been carried from one plant to the alternate host. The 

 unsatisfactory state of our knowledge of several species of the 

 genus Gymnosporangium is due in large part to the reluctance of 

 investigators to undertake a piece of work involving such a length 

 of time, and beset with difficulties such as they would be con- 

 fronted with in any attempt to carry back the infection from the 

 aecidial to the telial host. Plowright (17) and Arthur (i) appear 

 to be, so far as I have learned, the only persons who report having 

 carried such work through. 



If the Gymnosporangium is a perennial then the number of 

 years the telial host must be kept under strict control conditions 

 before inoculations are made is no less serious a question than the 

 time required to allow the rust to make its effects evident. 



In case Gymnosporangitim fraternum is confined to the leaves 

 of the cedar and is annual, the converse infections should not be 

 extremely difficult to get. If, on the other hand, the rust main- 

 tains itself in the wood tissues producing sori on new leaves each 

 year, or after a number of years on the trunk or branches, the 

 history of the successful experiment will be a long one. I have 

 undertaken to carry on some work along this line, and in recording 

 the results so far obtained I do not make any claim to have settled 

 the questions involved. 



Inoculation of Chamaecyparis with "Roestelia transformans on 

 Aronia" 

 Twenty-one cedars varying in height from four to tw^enty 

 inches w^ere brought from Newfield in April, 1914, and potted in 

 the soil in which they had been growing. Some of them were 

 heavily loaded with sori of G. fraternum at the time ; others had 

 only a few; eleven had none, so far as could be found. 



