24 BULLETIN 957, TJ. S. DEPARTMENT OF AGRICULTURE. 
which have been tested, the following are nearly immune: Eyath 
Nova, Franco-German, Holland (see also Tubeuf, 174), London, 
Rivers, Simcoe King. That is, plants tested under these names have 
so far shown themselves resistant, but not entirely immune. 
The cultivated gooseberries, varieties of Riles reclinatum in some 
cases more or less mixed with American species of gooseberries, are 
resistant but occasionally will become infected. 
Resistant species and varieties have been found reacting to the 
fungus and affecting it as follows : 
(1) Decreased number of uredinia and telia. 
(2) Above accompanied by reduction in size of uredinia and telia v\t.t!i lowered 
viability . 
(3) Small streaks and flecks of dead or dying tissue in infected leaves with 
uredinia and telia. (See PI. V, fig. 1.) 
(4) Small dead spots formed earl}- with very few or no uredinia and telia. (See 
PI. V, figs. 3 and 4.) 
This agrees essentially with the results of Stakman (149) with 
Puccinia graminis on resistant grains. 
LIFE HISTORY OF CRONARTIUM FJBICOLA. 
The Peridermium Stage on Pines. 
THE INCUBATION PERIOD ON PINES. 
According to European investigators, Oronartium ribicola has an 
indeterminate incubation period between infection of pine and pro- 
duction of secia. This varies from about two to four years, and 
possibly much longer. In one of Klebahus inoculation experi- 
ments he got pycnia! drops on young white pines 11 months after 
the inoculation (71). In another instance, infection probably 
occurred in 1887, pycnia were produced in 1888, and secia in 1889 
(65). Recently Tubeuf (174) reported the results of successful 
inoculations on Pinus strobus. Inoculations were made on Septem- 
ber 11, 1914; pycnia formed in July. 1915; they were also produced 
in 1916 in May and thereafter; ascia appeared in April, 1917. 
In North America considerable attention has been given to this 
matter. McCubbin (84) first attacked it by extensive studies of 
naturally infected trees. He concluded that five seasons were 
necessary for most of nearly 1,600 infections in Ontario to develop 
mature secia. He outlines tHe process as follows: first season, 
infection occurs; second season, dormant; third season, swelling of 
the bark; fourth season, swelling with pycnia; fifth season, mature 
secia. This makes a lapse of about three years and six months 
between actual infection and the formation of mature aecia. 
Stone (153) in 1917 studied this problem in a locality where the 
fungus was fruiting on white pines for the first time after infection 
occurred. The infection came from Ribes cynosbati, which in 1914 
was heavily infected. The Ribes plants were removed in the spring 
