1918] WEIR—RAZOUMOFSKYA 19 
much at variance with previous ideas of the host affinities of 
R. laricis, but they should not alter in the least the economic 
situation, since infections very rarely occur. The fact that both 
pines and larches are resinous may explain the occasional occur- 
rence of the parasite on the former hosts. Although great pains 
were taken to place the seed in favorable places on the trial hosts, 
the results on the following species were negative: Pseudotsuga 
taxtfolia, Pinus monticola, Picea Engelmanni, Thuja plicata, Tsuga 
heterophylla, Taxus brevifolia, Juniperus communis, Populus tremu- 
loides, P. trichocarpa, Betula occidentalis, Alnus tenuifolia, and 
_ Salix Bebbiana. Field observations on the intermingling of the 
branches of most of these species with severely infected branches of 
larch-bearing pistillate plants confirm the results of the cultures. 
Such observations, however, cannot be used as conclusive evidence 
for determining the host range for any one species of mistletoe. 
SuMMARY.—The hosts of Razoumofskya laricis are Larix occiden- 
talis, L. Lyalli, L. europea, L. leptolepis, Abies grandis, Pinus 
ponderosa, and P. contorta. The parasite is known to be of eco- 
nomic importance to the first named species only. The plant result- 
ing from an infection on any other host than that on which it 
normally grows exhibits considerable change in morphology and 
also in vigor. That different degrees of exposure with respect 
to light very greatly influence the color of the plants is very clearly 
demonstrated. 
Cultures with Razoumofskya species having purple flowers 
A group of small mistletoes found in the western United States 
has one character in common with R. pusilla of the East, namely, 
deep purple flowers.© They are R. Douglasii abietina (Engelm.) 
Piper? on Abies (figs. 11, 12), R. Douglasii (Engelm.) Kuntze on 
Pseudotsuga (fig. 15), and a small form on Picea (figs. 13, 14). A 
careful comparison of representative collections of these 3 plants 
from varied environments shows no constant characters by which 
they may be held as distinct species. All three have 2, 3, or rarely 
° Wer, J. R., Wallrothiella Arceuthobii. Jour. Agric. Research 4:372. 1915. 
7 Reported e ENGELMANN under the name Arceuthobium — var. abietinum 
in S. Watson, Bot. Cal. 2:106. 1880. 
