32 BULLETIN" 360, U. S. DEPAETMEISTT OF AGRICULTURE. 



Ra.zoumofskya douglasii (Engelm.) Kuntze is of economic impor- 

 tance only on the Douglas fir. The affinities of the very small and rare 

 forms of Razoumofskya on spruce and fir/ described by Engelmann 

 (6, p. 253) under the name of Arceuthohimn douglasii var. micro- 

 carpum for the former host and A. douglasii var. abietinum (3, v. 2, p. 

 106) for the latter, are not definitely established. In point of time of 

 blooming and seed maturity, it coincides with that of Razoumofskya 

 douglasii for northern regions, and their form and color are quite 

 similar, especially the color of the staminate flowers. These small 

 plants, together with the Douglas fir mistletoe, are the only mem- 

 bers of the genus exhibiting a pronounced color of the lobes, which 

 are a bright, deep purple. Until cross-inoculation experiments are 

 perfected, these particularly small mistletoes on spruce and fir may 

 be considered wholly unimportant from a silvicultural standpoint. 

 For the sake of convenience, they may be placed with the Douglas 

 fir mistletoe and the whole designated as the Pseudotsttga-Ahies- 

 Picea group, characterized by their small size and colored flowers. 

 Razoumofskya laricis Piper, the most universally distributed and 

 probably the most injurious of the entire genus, is associated with 

 the western larch. This species in a single instance has been col- 

 lected by the writer on lodgepble pine near Missoula, Mont. It is 

 a significant fact that this infection is not vigorous and appears to 

 be dying out. R. americana (Nutt.) Kuntze is more strictly asso- 

 ciated with the lodgepole pine, but is the cause of serious damage to 

 the jack pine {Pinus hanksiana) where these two species approach 

 each other in Canada. R. tsugensis Eosend., as far as observations 

 in the field have gone, is confined to the hemlocks. 



The remaining species of importance may be divided into two main 

 groups, a fact that has not been heretofore set forth, viz, those associ- 

 ated with the soft or white pines and those attacking the hard yellow 

 pines. It seems that the members of one group are not in a single in- 

 stance associated with the hosts of the opposite group. The former 

 group includes the following specie,s and hosts : Razoumofskya divari- 

 cata (Engelm.) Coville on the nut or piiion pines, P. edulis and P. 

 monophylla (6, p. 253) ; R. cyanocarpa A. Nels. on P. flexilis (4, p. 146) , 

 P. alhicaulis, and P. Tnonficola. Pinus mo7iticola has not been previ- 

 ously reported as a host for these parasites. Plnus strohiformis^ the 

 Mexican white pine, is reported (11, p. 65) as the only host of R. hlu- 

 meri (A. Nels.) Standley. The second group may be included by the 

 two-form species: R. campylojjoda (Engelm.) Piper and R. crypto- 

 poda (Engelm.) Coville. The fornler is principally injurious to Pinus 

 ponderosa^ but is common on P. attenuata (7, p. 366; 13) aiid P. 

 jeffreyi (10, p. 38). The latter is likewise an injurious parasite on 



^AMes concolor is also host for Phoradendron hoUeanum (Seem.) Eichl. (5, p. 193). 



