rg18] WEIR—RAZOUMOFSKYA 15 
Cultures show that the plant known as R. occidentalis abietina on 
Abies is in all probability a biological form of R. campylopoda. 
The taxonomic position of 
the plant, however, cannot 
be established with any 
certainty until it is success- 
fully grown on yellow pine. 
Cultures with larch mistletoe 
From the fact that this 
parasite, R. laricis Piper 
(figs. 9, 10), exhibits con- 
siderable variation under 
different conditions of growth 
and will occasionally grow on 
other hosts than Larix, it 
seemed desirable to study the 
species in culture. The chief 
results of these experiments 
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Fic. 9.—R. laricis on Larix occidentalis: 
staminate and pistillate plants. 
are embodied in table II. These results indicate that Larix is the 
true host genus for R. Jaricis. 
Fic. 10.—R. laricis on Larix occidentalis: pistillate 
plants; uaa one-half, 
The fact that 6 trees of Larix 
occidentalis were in- 
fected out of 6 on 
which seed were sown 
demonstrated the close 
affinity of the host and 
parasite. The readi- 
ness with which R. 
laricis infects Larix 
europea and L. lepto- 
lepis, the common 
Japanese larch, shows 
that this parasite may 
be expected to cause 
serious injury to plan- 
tations of these species not only in America, but in many parts 
of Europe and Japan as well, wherever climatic conditions are 
