ECONOMIC IMPORTANCE OF FUNGI 301 
1892, is common in the plant houses of commercial 
florists. 
287. Pine Tree Blister-rust. Among the more im- 
portant plant diseases recently appearing in the United 
States is the pine tree blister-rust, introduced from 
Europe about 1909. One species is Cronartium pyri- 
forme, which is the telial stage of Peridermium pyriforme. 
The aecial stage (Peridermium) appears on the pine, 
while the alternating host is the "false toad-flax" (Com- 
andra umbellata and C. pallida). 1 This fungus attacks 
species of pine that have less than five leaves to the fascicle, 
such a.s Pinus contorta, P. ponderosa, and P. rigida. 
Another species (Cronartium ribicola) passes its aecial 
stage on five-leaved pines, where it is commonly known 
as Peridermium Strobi; 2 the telial stage, as its name in- 
dicates, is passed on species of Ribes (gooseberries and 
currants) (Fig. 222). 
The importance of such a disease as this may be inferred 
when we consider that the value of the white pine grow- 
ing in the New England states is estimated at $75,000,00x3. 
that of the Lake states at $96,000,000, of the Western 
states at $60,000,000, and of other National forests at 
$30,000,000, a total of $261,000,000. The western sugar 
pine (Pinus Lambertiana) has a total value estimated at 
$150,000,000. Thus, timber to the value of $411,000,000 
is threatened with destruction by this one parasitic dis- 
ease. In order to reduce the danger of infection from the 
blister-rust, and also from the pine-shoot moth (Evetria 
1 The Comandra is itself a parasite on the roots of various species of 
blueberry (V actinium), and other woody plants. 
* From Slrobus, the specific name of the common white pine (Pinus 
Strobus}. 
