NATURAL REGENERATION OF DOUGLAS FIR, 1B 
len grains of forest. trees may be carried as far as 80 or 90 miles by 
wind.’ The method of pollination is an important factor in the seed 
production of trees that are left after logging or after a forest fire. 
Diseased trees are known to produce only about three-fifths as much 
good seed as sound trees.° The smaller amount of good seed pro- 
duced by diseased trees may be due to the infertility of the pollen. 
If diseased trees only were left on an area, the quantity of good seed 
produced would be small, and that might be a serious factor in seed 
production. However, if some diseased trees were left on a cutting 
area, and if a stand of Douglas fir remained in the surrounding ter- 
ritory, there would always be a chance of fertilization with pollen 
produced by sound trees. In that event the seed production would 
not be seriously handicapped. 
The average mature Douglas fir tree produces about 40,000 seeds 
per crop. There 1 1s a wide variation in seed production due to the age, 
size, and health of the tree, density of stand, soil, latitude, and alti- 
tude. Each of these factors influences seed production, although the 
direct effect of each individual factor can not be definitely stated. 
Trees 100 to 200 years old bear most prolifically. It was found that 
the average 15-year-old tree produced 4,000 seeds, the average 100 
to 200 year old tree produced 40,000 seedsy and the average 600-year- 
old tree produced 7,000 seeds. At elevations of 300 to 600 feet. above 
- sea, level the average tree produced about 34,000 seeds per crop as 
compared with 4,000 seeds for the average tree at 3,000 to 4,000 
feet above sea level. The effect of latitude is noticeable even within 
the hmits of Oregon and Washington. The average tree in central 
Oregon produced 35,000 seeds per tree, but a comparable average 
tree in northern Washington produced only 7,000 seeds. This, ap- 
parently, is a wide variation and may not be consistently maintained 
during each seed crop, but the figures indicate that latitude has a 
marked influence on seed production. The effect of the health of 
the tree is very noticeable. Diseased trees that were severely 
affected produced 7,700 seeds per tree, but sound trees of the same age 
class and same locality produced 14,200 seeds. In the check taken 
there was little effect in quantity production of seed that could be 
traced directly to soil conditions. The quality of the seed was the 
noticeable varying factor. Trees on poor soil produced only two- 
thirds as many good seeds as trees on good soil. 
Another factor which must not be overlooked in seed production 
in Oregon and Washington is the damage done by the insect 
Megastigmus spermotrophus Wachtl. This insect is always present 
and attacks some of the seed, but in a light seed year concentrates 
its attacks and becomes most destructive. For this reason a sparse 
seed crop in Douglas fir is usually equivalent to a failure. 
A careful examination of the cones before the seed matures during 
July and August will usually reveal immature stages of the seed- 
infesting insects. If cones of the past season are examined during 
the winter and spring, they will indicate whether or not the area 
is infested by these insects. 
8 Hesselman, Henrik, Iakttagelser Over Skogstridspollens Spridningsf6rmaga (Dissemi- 
nation of Pollen from Forest Trees). Meddel. Statens Skogsférséksanst, 16: 27-60. 
® Wil C. P.. and Hofmann, J. V. A Study of Douglas Fir Seed. Proceedings of the 
Society. ‘of American Foresters, Vol. X, No. 2, pp. 141-164. 1915. 
