32 BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. 
Razoumofskya 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 Arceuthobiwm douglasii var. micro- 
carpum for the former host and A. douglasii var. abietinum (8, 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 Razowmofskya 
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 Pseudotsuga-A bies- 
Picea group, characterized by their small size and colored flowers. 
Razoumofskya laricts 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 lodgepole pine near Missoula, Mont. It is 
a significant fact that this infection is not vigorous and appears to 
be dying out. L&. americana (Nutt.) Kuntze is more strictly asso- 
ciated with the lodgepole pine, but is the cause of serious damage to 
the jack pine (Pinus banksiana) where these two species approach 
each other in Canada. f. tsugensis Rosend., 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 
eroups, 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 species and hosts: Razoumofskya divari- 
cata (Engelm.) Coville on the nut or pinion pines, P. edulis and P. 
monophylla (6, p.253) ;R. eyanocarpa A. Nels. on P. flexilis (4, p. 146), 
P. albicaulis, and P. monticola. Pinus monticola has not been previ- 
ously reported as a host for these parasites. Pinus strobiformis, the 
Mexican white pine, is reported (11, p. 65) as the only host of R. blu- 
meri (A. Nels.) Standley. The second group may be included by the 
two-form species: RP. campylopoda (Engelm.) Piper and PF. erypto- 
poda (Engelm.) Coville. The former is principally injurious to Pinus 
ponderosa, but is common on P. attenuata (7, p. 366; 13) and P. 
jeffreyi (10, p. 88). The latter is likewise an injurious parasite on 
14 bies concolor is also host for Phoradendron bolleanum (Seem.) Hichl. (5, p. 193). 
