116 Journal of the Mitchell Society [June 



related the rusts of apples, quinces, haws, e^e., that cause much 

 damage in the South Atlantic states and which infest the red cedar 

 as their alternative host. We have chosen three species of these cedar 

 rusts to represent the group of rusts in this paper. They belong to 

 the genus Gymnosporangium in the family Aecidiaceae. 



GYMNOSPORANGIUM 



Producing on cedar in wet weather in the spring conspicuous 

 masses of yellowish jelly either directly on the twigs, branches, or 

 main trunks or on special large galls on the small twigs. This jelly 

 contains a large number of two-celled spores, called teleutospores or 

 teliospores, which sprout at once in the jelly to form elongated 

 basidia, called promycelia, which are divided into four cells by 

 cross walls, each cell sprouting to form a smaller curved spore called 

 a sporidium. These last are then blown about and falling on leaves 

 or fruits of apples or their relatives may infect them and produce 

 in a few months discolored yellowish spots which produce on the 

 underside tubular projections in which are borne in chains another 

 kind of spore called the aecidiospore or aeciospore composed of one 

 cell with a warted wall. These when blown back to the young cedar 

 will infect the leaves and cause the development of the large galls 

 again which are full grown and produce spores the second spring 

 after the infection. The life history of these rusts thus requires two 

 distinct hosts and each must be infected by spores borne on the other. 

 On the upper side of the infected spots on the apple, etc., are borne 

 in sunken flasks very small jiycniospores which have no known func- 

 tion. Of the many species of the genus we select three that are found 

 in Chapel Hill. 



In addition to the treatment in North American Flora and in the 

 texts mentioned, where references are gi'S'en, one may refer to de- 

 tailed work by Heald on the life history of the apple-cedar rust in the 

 22d Rep., Nebraska Agr. Exp. Station, p. 105, 1909 ; also a paper by 

 Coons in the same series 25th Rep., p. 217, 1912. 



Key to the Three Species Treated 



All forming gelatinous excrescences on cedar (/. virgiiiiuna) in spring. 

 P^orming globular, uneven balls which vary in size 



from a pea to a small ai:)ple, from Avhich long 



gelatinous processes arise G. Jutiiperi-rirgiiiianae (1) 



Forming rough and usually thickened areas on twigs 



