CURRANT DISEASES 215 
After the spores escape, a whitish membrane is left about the 
edges of each pustule (Fig. 57); this disappears by the first of 
June and an empty depression remains. Affected trees are 
stunted: the tops have a peculiar bunched growth, the past 
season’s growth is 
shortened, and fi- 
nally the needles 
turn yellowish in 
color. 
Cause of Euro- 
pean rust. 
This rust fungus, 
Cronartium Ribicola, 
like many others, 
is hetercecious; 
that is, it requires 
two distinct kinds 
of hosts for its full 
development. And 
during its life-his- Fic. 56. — European currant-rust; telia on lower 
tory five  spore- surface of black currant leaf. 
forms are devel- 
oped. The fungus attacks and lives in the bark of the 
white pine in one stage of its life-history; as such it is 
known to scientists as Peridermium Strobi. It may also occur 
on other five-needle pines, such as the stone-pine (Pinus 
Cembra), sugar-pine (Pinus Lambertiana), western white pine 
(Pinus monticola), and Himalayan white pine (Pinus excelsa). 
The white pine (Pinus Strobus) is found in North America 
from Newfoundland to Pennsylvania, along the Appalachians 
to Georgia, west to eastern Iowa and Minnesota; in Canada 
from Lake Winnepeg to the northern shore of the St. Lawrence 
Gulf and Newfoundland. In the other stage, the fungus lives 
in the leaves of about twenty-five different species of wild and 
