NATURAL REGENERATION OF DOUGLAS FIR. 15 
agencies, the immediate replacement of that forest depends upon the 
available supply of seed.11_ The species that is able to restock the area 
first may hold it through several generations or permanently, but to 
cdo so it must have a supply of seed at hand. There is no more imme- 
diate supply of seed than that stored in the forest floor, and the 
species that has a supply of stored seed takes possession of the area. 
In order to have a supply of stored seed, seed production and distri- . 
bution are essential, but the viability of the seed is even more i1m- 
portant. Seed may be stored, but if it does not retain its vitality it 
is of no avail to the species in replacing a forest. The condition 
found in the forest floor is shown in Plate I, Figure 2. 
RESISTANCE OF DOUGLAS FIR SEED TO HEAT. 
To find what temperature would kill Douglas-fir seed, lots of 200 
seeds each were subjected for 10 hours to dry oven heat at tempera- 
tures from 100° to 300° F. Another series of tests, with temperatures 
varying from 100° to 240° F., was made in an oven in which the air 
was kept as nearly saturated as possible with water vapor. 
| Table 5 shows the germination from seed which was subjected to 
| these heating tests. 
TABLE 5.—LHffect of heat on germination of Douglas-fir seed. 
Degrees Fahrenheit of heat applied for 10 hours. 
not a is 
Mea ted 100 140 160 180 200 | 220 240 
CO aouopocoboucebood soduedee 55 64 62 61.5 73 0.5 0 
0 
y 0 
Moistiheate s2ccen 2 ee ek sok. 55 65 60 24 0 0 0 
Douglas-fir seed will withstand a dry heat up to 200° F. and a 
moist heat. up to 160° F. for long periods. The effect of heat upon 
the seeds was studied with the microscope. No changes could be 
noted until the temperature was raised to within about 40° F. of the 
temperature that killed the seed. When this point was reached the 
endosperm began to darken, oils exuded, and the outer seed coat 
dried very noticeably. With the higher temperature the other seed 
coats also showed effects of drying. The intensity of all these changes 
was directly related to the degree of heat applied. 
In the forest floor the stored seed is, of course, surrounded by 
different conditions from those of the oven. In order, therefore, to 
ascertain the degree of protection afforded to seed during a slash 
fire Douglas-fir seed was artificially stored in four locations in a 
heavy Douglas fir-cedar-hemlock slash near the Wind River forest 
experiment station. The stations were selected in mineral soil in 
the middle of a skid road, in a rotten log, in mineral soil under duff, 
and in the duff. Temperature readings were taken at each station 
during the fire. The slash was burned on June 27, 1919, with a very 
hot fire, and resulted in as clean a burn as may be expected in this 
type of slash. (PI. IT.) 
1 Hofmann, J. V. How Fires Destroy Our Forests. American Forestry, vol. 26, 
June, 192f, 
