12 BULLETIN 957, tf. S. DEPAETMEHT OE xiGEICULTUEE. 



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 Pinus. 



Section Haploxylon. 

 Subsection Cembra. 

 Group I. Cembrge. 

 Jcoraiensis +. 

 cembra +. 

 alhicaulis. 

 Group II. Plexiles. 

 flexilis +. 

 armandi. 

 * Group III. Strobi. 



ayacahuite (or strobiformis) +. 

 lambertiana +• , 

 -parviflora +. 

 -pence +• 

 excelsa +. 

 monticola +. 

 strobus +• 

 Subsection Paracembra. 



Group IV. Cembroides — pinon pinea. 

 Group V. Gerardianag — pifion pines. 

 Group VI. Balfouriange. 

 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 vv^ay. 



Inoculations of Cronartium Riblcola 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 moculated 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 strohus trees by suspending telia-bearing leaves of Rihes nigrum 

 above the trees and covering them with a large bell jar. On June 19, 



