GYMNOSPORANGIUM JUNIPERI-VIRGINIANAE 515 



teleutospore-sori.i Each sorus is composed of many two-celled 

 teleutospores embedded to a greater or less degree in a gelatinous 

 matrix derived from the teleutospore-pedicels. Under favourable 

 weather conditions, with sufficient moisture, the sori swell up into 

 large reddish-brown gelatinous horns on the exterior of which are 

 numerous teleutospores (c/. Figs. 207, 208, 209, and 210). Each of 



Fig. 208. — Gymnosporangium J uniperi-virginianae on Juniperus virgin- 

 iana. Two Cedar apples (rust galls) of medium size with expanded 

 gelatinous teleutospore-sori. Photographed by N. J. Giddings. 

 From Bull. No. 170, of the West Virginia Agricultural Experiment 

 Station. About natural size. 



the two cells of a teleutospore may send out a basidium (promy- 

 celium).2 Each basidium becomes divided by septa into five cells, 

 a sterile stalk-cell and four other cells each of which develops a 

 sterigma and a basidiospore (Fig. 21 1).^ As first observed by 

 Coons,^ the basidiospores, when ripe, are violently discharged from 

 their sterigmata into the air. 



^ N. J. Giddings, " Infection and Immunity in Apple Rust," West Virginia 

 Agricultural Experiment Station, Bull. 170. 1918, p. 9. 



^ Ibid. 3 jj g ;Rggj ^^^ Q jj Crabill. loc. cit., p. 27, Fig. 8. 



■* G. H. Coons, " Some Investigations on the Cedar Rust Fungus, Gymnospor- 

 angium Juniperi-virginianae," Annual Report No. 25, Nebraska Agricultural 

 Experiment Station, 1912, pp. 217-242. 



