WHITE-PINE BLISTER RUST. 
13 
1904, the pines were examined. At that time some of the new shoots 
bore abnormal leaves of a juvenile type singly, instead of in fives. 
The new twigs were abnormally pale in color. Many of the leaves 
of the growth of the previous year were spotted with yellow through 
their entire thickness. These yellow spots were especially plentiful 
near the base of the leaves. Microscopic examination showed abun- 
dant mycelium to be present in the yellow areas. Later pycnia devel- 
oped on the twigs near the bases of the spotted leaves. 
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Fig. 10.— Outline map of the northeastern part of the United States, showing (by black dots and cross 
hatching) the known distribution" of white-pine blister rust in North America to and including 1916. 
In 1914, Tubeuf (174) inoculated trees of Pinus strobus, P. lam*- 
bertiana, P. cembra, P. cembroides, P. excelsa, P. pence, P. parviflora, 
P. Jlexilis, and P. montezumae with sporidia of Cronartium ribicola 
under controlled conditions. In 1917, secia were produced on some 
of the P. strobus. Yellow spots were produced on the leaves of P. 
lambertiana, but no further development of the fungus occurred. 
Spots which were doubtfully caused by the fungus were noted on P. 
cembroides. No other species became infected. Infections were 
produced directly on the juvenile leaves, on mature leaves, and 
through the epidermis of the lengthening buds of the young shoots. 
In North America, the writer seems to have been the first to 
inoculate successfully young Pinus strobus trees with sporidia (133, 
134). The inoculations were made both with and without wounds 
in the young bark, telial columns being used for inoculum. Pycnial 
drops were produced by one tree unwounded and by one which was 
