20 



BULLETIN 034, U. S. DEPARTMENT OF AGRICULTURE. 



nurseries in Illinois and Minnesota were obtained from the nursery- 

 men by Mr. R. G. Pierce and are indicated by the initial " P." In- 

 formation obtained directly from the nurserymen by the writer is in- 

 dicated by " N." For nurseries where the statements are based on 

 the writer's personal observation rather than on the authority of the 

 nurserymen, his own initial ( u H ") is given. Most of the writer's 

 own estimates of relative susceptibility are based on a comparison 

 of detailed counts of the damped-oif seedlings in a large number of 

 untreated plats at different times, as well as on observation. The 

 nurseries on which Tillotson reported were all west of the Missouri 

 Eiver, most of them being in the mountain region. The reports in- 

 dicated by "H" and "N" were mostly from nurseries -east of the 

 Rocky Mountains. In cases in Avhich the data permit it, the species 

 are classified as most susceptible, intermediate, least susceptible, or 

 immune. In a number of cases, however, it is only possible to classify 

 them as " more " or " less " susceptible. 



TABLE II. Relative susceptibility to dam ping-off of different conifer species. 



[Figures in parentheses in this table indicate the number of nurseries from which the susceptibility noted 

 has been reported by the observer to whom the preceding letter refers.] 



a Host names for American species follow the usage in the publications and a later verbal communication 

 of Mr. George B. Sudworth. of the United States Forest Service. For exotic species the Standard Cyclo- 

 pedia of Horticulture, New York, 1916, edited by L. H. Bailey, is taken as the standard. The classification 

 follows Saxton (118). 



b Symbols signifying the authority for the report: B=Boerker (13). Bu=Biittner (25, 26), Bp= Bates 

 and Pierce (7), C=Clinton (28), H= Writer's estimate, N= Nurserymen's estimate (obtained by the writer), 

 Nb=Negerand Biittner (94), Ne=Neger (93), P= Nurserymen's estimate (obtained by Pierce), T= Forest 

 officers' estimate (compiled by Tillotson, 139). 



c Susceptibility to Phytophthorafagi. 



