MISTLETOE INJURY TO CONIFERS. oe 
P. ponderosa, but occurs on P. jeffreyt (5, p. 192), P. arizonica (2, 
p- 248), and P. mayriana (2, p. 248). FR. campylopoda has recently 
been collected by the writer near Coeur d’Alene, Idaho, on P. contorta. 
Sparingly distributed throughout the Northwest are some large forms 
of Razoumofskya on Abies. Plants collected by the writer on Abies 
grandis and A. concolor are apparently the same as that described by 
Engelmann (3, v. 2, p. 106) on the former host under the name 
Arceuthobium occidentale var. abietinum. Although it would prob- 
ably be better on morphological grounds to refer this form to 
R. campylopoda (Engelm.) Piper, as Engelmann’s Arceuthobium 
occidentale 1s now named, owing to its seeming close affinity to 
the genus Abies and the absence of cross-inoculation data it could 
well be raised to specific rank. These mistletoes in point of mor- 
phology are in great contrast with the small forms on Abies previ- 
ously mentioned. They may be considered typical of a group of 
large forms occurring only on Abies. 
From the foregoing, it seems possible that the members of the genus 
Razoumofskya may be arranged in a series of natural groups accord- 
ing to their host relationships. It is also interesting to note that the 
largest, the longest lived (both cortical and aerial parts), and the 
most strictly parasitic forms are associated with the hard or yellow 
pines. These pines exhibit anatomically a high differentiation. This 
may throw some light on the nutrient relation of some mistletoes 
to their hosts; also their family peculiarities. 
SUGGESTIONS FOR CONTROL. 
Tt is clear from the foregoing pages that the damage to forest 
orowth by the mistletoes of coniferous trees in the Northwest is of 
sufficient importance to receive the attention of every forester. Steps 
should be taken in all logging operations, where local problems of 
economy do not interfere, to make a beginning of the eradication of 
mistletoe by marking every infected tree for cutting. In some cases it 
would seem advisable to introduce into the contract a special clause 
dealing wholly with mistletoe-infected trees. The most injurious of 
the mistletoes of the genus Razoumofskya on coniferous trees, as indi- 
cated, are in the main confined to their own particular hosts or to spe- 
cial groups; hence, it is not advisable to establish in mistletoe regions 
pure stands of a species much subject to attack. In this respect the 
problem of the control of mistletoe is similar to that of forest-tree 
fungi. Mistletoes being light-loving plants, close stands should be 
maintained as much as possible on all exposed parts of the forest. 
For the same reason rims of canyons and all exposed areas, such as 
the borders of bench lands, natural parks, shores of lakes, etc., should 
be protected with species which are not usually subject to the ravages 
