12 BULLETIX 957, XT. S. DEPARTMENT OF AGRICULTURE. 
Sudworth (154) recognizes eight species of the white pines (exclu- 
sive of the pinon pines) for North America (fig. 2) but does not treat 
those of the Old World. Shaw (126), who treats the pines of the 
world, also recognizes eight North American species of white pines. 
He is, therefore, taken as the authority for the pines in this bulletin. 
The white pines of the world are grouped by Shaw as follows : 
Genus Finns. 
Section Haploxylon. 
Subsection Cembra. 
Group I. Cembrse. 
l;oraiensis -f- 
cembra +. 
albicaulis. 
Group II. Flexiles. 
flexilis +. 
armandi. 
Group III. Strobi. 
ayacahuite (or strobiformis) +. 
lambertiana +. 
parviflora +. 
pence +• 
excelsa +. 
monticola +. 
strobus +. 
Subsection Paracembra. 
Group IV. Cembroides — pinon pines. 
Group V. Gerardianse — pinon pines. 
Group VI. Balfourianse. 
balfouriana. 
aristata-\-. 
In examining the above synopsis, note the grouping of the known 
susceptible species (which are indicated by + ) especially in the first 
three groups which make up the subsection Cembra. Investigations 
of outbreak areas in Europe where the various species of pine have 
been present might yield on this point most interesting and valuable 
information which can be obtained in no other way. 
Inoculations of Cronartium Ribicola on Pines. 
Klebahn (68, 71) appears to be the first European investigator 
who has inoculated pines with Cronartium ribicola and who has pub- 
lished his results. He inoculated young Pinus strobus trees with 
pycnospores, but with no success (70, p. 387) . Inoculations made by 
him with sporidia in 1888 were rendered worthless because the pines 
were probably infected naturally before the test was made (71). On 
August 27, 1903, Klebahn (71) made inoculations on two young 
Pinus strobus trees by suspending telia-bearing leaves of Ribes nigrum 
above the trees and covering them with a large bell jar. On June 19, 
