WEYMOUTH PINE RUST 233 



Marshall Ward, Sessional Papers, xvii., Colombo, Ceylon, 

 1881. 



WEYMOUTH PINE RUST 



(Cronartium ribicolum, Deitr. 

 = Peridermtum strobi, Kleb.) 



The aecidium stage of this fungus occurs on living bark 

 of the Weymouth pine (Pinus strobus\ and has also been 

 recorded as occurring on Pinus lambertiana and P. 

 cembro. The large aecidia burst through the bark in 

 considerable numbers, are pale yellow, and contain 

 minutely warted, subglobose, orange spores. These spores 

 when placed on living leaves of the black currant (Ribes 

 nigrutn), also JR.. aureum and R. alpinum, germinate and 

 produce, in the first instance, crowded pustules of uredo- 

 spores ; afterwards, from the centre of each uredo pustule, 

 a very slender, hairlike body about one line long springs 

 up, composed of a mass of teleutospores, which germinate 

 without falling away ; each teleutospore gives origin to one 

 germ-tube which bears three or four minute secondary- 

 spores near its tip. These secondary spores in turn give 

 origin to the aecidium stage on pine bark. Spermogonia 

 alone are formed the first year after infection, the aecidia 

 the following year. The stage on currant leaves was at 

 one time considered as an independent fungus called 

 Cronartium ribicolum. 



It is somewhat remarkable that, so far as at present 

 known, this fungus is absent from America, the home of 

 the Weymouth pine. 



PREVENTIVE MEANS. Requiring the two hosts for its 



