THE WESTERN YELLOW PINE MISTLETOE. Zo. 
of the parent tree which may be transmitted through the seed, such 
as an unusual divergence from the typical silvical characteristics of 
the species. A clearer conception of the latent possibilities of dis- 
ease resistance and immunity of a species obtained through tree 
‘breeding is of vast importance in the silvicultural improvement and 
management of the forest. The hereditary influence of the parents 
upon the offspring is a well-recognized factor in genetics. This factor 
is doubly important in forestry, not only in the collection of seed for 
artificial regeneration, but also in the selection of seed trees to provide 
for the natural reproduction of cut-over forests. In timber-sale prac- 
tice only thrifty seed trees should be left and all diseased and sup- 
pressed trees should be removed in order to improve the condition of 
the forests of the future. 
SILVICULTURAL ASPECT OF MISTLETOE INFECTION. 
The destruction caused by disease promises to approach or even 
surpass the losses from fire on the national forests of the Southwest, 
now that the development of fire protection has reduced the fire 
hazard. Mistletoe injury presents one of the most serious phases of 
this silvicultural preblem. The parasite may be slow in effecting its 
injury, but it is unquestionably sure. 
A brief discussion of some of the salient objects of silviculture is 
essential to a complete understanding of the significance of any 
methods of control which may be attempted. The chief fundamen- 
tals of silviculture, as applied in the regeneration of western yellow 
pine stands, are to maintain the continuity of the forest and to 
increase its productivity. A number of basic considerations must 
be taken into account under any rational method of cutting, among 
which may be mentioned the silvics of the species, the fire hazard 
and liability, exploitation and economic conditions, and the removal 
of the decadent, unhealthy, and overmature timber as rapidly as 
possible, to avoid waste through decay. All defective, diseased, and 
_ suppressed trees should be marked for cutting unless needed as fire 
_ insurance or seed trees. No defective or diseased tree should be left 
standing if it is evident that it will not live until the next cutting, 
unless it is absolutely required for silvicultural purposes. When it 
becomes necessary to reserve trees among the large diameter classes, 
_ thrifty, healthy trees of good form should be selected, since the con- 
- dition of the progeny is influenced by heredity as well as by soil and 
climate. Increased forest productivity will be realized if, in the 
application of the above principles, the forester will also strive to 
eliminate the deterioration of merchantable material. It is thus. 
evident that the marking on each individual area must be varied to 
meet the silvicultural requirements of the forest. The importance 
_ of careful, intelligent marking on timber-sale areas can not be over- 
