MISTLETOE INJURY TO CONIFERS. 7 
the nodes and the basal scales of the terminal buds, are the chief 
factors in the penetration of the primary root. 
The occurrence of mistletoe plants on the thick-barked branches of 
old trees or on the main trunk are the result of earlier infection, 
when the bark was thinner. What appears to be a recent infection 
on the older parts of trees is often merely a retarded or suppressed 
condition of an earlier in- 
fection which has  ex- 
pended most of its energy 
in the production of a sub- 
cortical stroma and later 
breaks through the bark. 
Periods of suppression and 
dominance are frequently 
noticeable in all mistle- 
toes, a condition noted to 
be in several instances di- 
rectly referable to the 
state of vigor of the host. 
An excessive flow of resin 
sometimes appears in the 
second and third year of 
the hfe of a new infection 
on larch and yellow pine, 
which, if not fatal to the 
young plants, may seri- 
ously retard their growth 
for years. Until infection 
by actual inoculation, 
using natural methods, is 
attained, all statements of 
the ability of the parasite 
Fic. 5.—Four-year-old yellow-pine seedlings killed by 
; mistletoe. Note the hypertrophy of the stem at 
to effect an entrance i1n the point of infection and the shortening of the 
a needles. The two seedlings on the right were 
old barked branches or killed principally by having the wood and cambium 
trunks can not be accepted in the swelling infiltrated with pitch. The para- 
site killed the seedling on the left by invading the 
and must be considered toeinat ee 
faulty observation. The 
writer has never succeeded in causing the infection of branches at any 
point older than four years. The ease of infection is found to be 
more or less in proportion to the decrease in age of the branches 
tested. This was proved in the case of yellow pine by inserting 
seeds at regular intervals in the axils of the leaf sheaths of young 
branches, from the terminal bud to the tenth internode. The results 
of this experiment are shown in Table ITI. 
