.-,(! 



«'1:oxai:tiim ribk OLA 



of Ribes (Fig. 34); they have been recorded on 2(j < »ut of about 

 50 known species. The speroiogones and secidia are formed on 

 stems and branches of the five-leaved species of Pinus: they 

 have been found on five out of the eighteen Pines of that group, 

 bul do not attack species having 2 or 3 leaves in a fascicle 

 The following account is founded on that of Spaulding (1911). 



The h.oidiospores are formed about the beginning of August . 

 and if they are blown by the wind, and adhere to moist young 

 branches of the Pine, the germ-tube enters and products ;i 

 mycelium which lives in the branch for several years, ultimately 

 causing it to become considerably swollen in a fusiform or 

 irregular manner. In about half the cases it is the main trunk 



Fig. 34. Cronartium ribicola. a, a spore of Peridermiwm Strobi, x 60o ; 



b, the teleutospore-columns on leaf of Bed Currant (reduced) ; c, a uredo- 

 spore; d, top of a column of teleutospores, x600. 



that is infested. On this swollen portion spermogones appear 

 at almost any period of the year, followed in spring by the 

 secidia, which break through fissures in the bark ; these may 

 be even as much as 1 cm. high, yellowish-white in colour, with 

 orange spores. When the peridium bursts open, in an irregular 

 manner, the spores may be carried by the wind to an}' plants 

 of Ribes that may be near and can at once infect them. The 

 distance to which the aecidiospores can be effectively carried is 

 estimated to be less than 500 ft. These spores cannot infect 

 the Pine ; but if they fall upon a moist leaf of Ribes, the uredo- 

 pustules usually appear, on the underside, in from 10 to 20 days. 

 These uredospores can, as usual, reproduce themselves on 



