17 
NATURAL REGENERATION OF DOUGLAS FIR. 
VIABILITY OF SEED IN THE FOREST FLOOR. 
In order to obtain records under controlled conditions of the 
longevity of seed in the forest floor an experiment was initiated in 
the summer of 1916. Thirty cages, 36 by 12 by 6 inches in size, of 
galvanized wire of 4-inch mesh, were used. Seed mixed with litter 
and duff was placed in the cages, which were then closed to exclude 
rodents, and placed in the forest at different localities. About 8,000 
Douglas-fir seeds were stored in each cage. 
In the spring of 1917 three of the cages were taken up and germi- 
nation tests were made of their contents. A germination of about 
15 per cent was secured during the summer of that year. When the 
cages were examined in place in the forest on July 6, 1917, it was 
found that rodents had dug around them in the attempt to get to the 
seed, and the burrows in many cases were left open. Along the 
edges of these burrows, where aeration and warmth had reached 
the seed in the cages, a vigorous germination was noted. Germina- 
tion tests in 1918 of this same seed resulted in very few seedlings, and 
no germination was secured from the stored seed in later years. 
This experiment proved conclusively that through the first year 
the seed in the forest floor remains sufficiently viable to produce good 
stands of reproduction and that some seeds remain viable until the 
second season. It is also known that seed remains viable in the 
forest floor much longer than two years and still produces good 
stands of young growth. The failure of germination in this experi- 
ment may be attributed to the artificial conditions of storage as com- 
pared with the condition of seed stored by rodents or in the cones. 
_Seed stored in the cones at the time of ripening or later is under 
more favorable storage conditions, especially in the matter of pro- 
tection from fire. Before the cones open, their scales afford effective 
protection to seed exposed to forest or slash fires. Cone scales are 
excellent insulation while the cones are still sealed, for a hot fire of 
short duration does not open the cones and the seeds escape the fire. 
The resistance to heat of seeds in unopened cones is shown in Table 8. 
TaBLeE 8.—LHffect produced on Douglas-fir seed by the heating of the cones.’ 
Temperature in degrees Fahrenheit inside of | Percent- 
cone after exposure for the indicated number | 48° of | Percent- 
of minutes. weight | age of 
Temperature outside of cone. lost in | germina- 
moisture | tion of 
| during seed. 
1 3 5 6 7 10 11 15 | heating. 
Core 
CST Cape as MRP es te SU SOON a ee SHA al ay Nese ill pea WS egeeee 183 | 190 50.3 54 
SE Pe eee emai te Savere apn ag seme [ Oe Sil | eee eters 20 eee NG yz |Przen ees 210 56, 1 61 
SOU Aes Se Ws Ve Aue aN aD whe ee SOE Leesa) 52 See Oe eeoe LZO RE S228 230 55. 0 Ol 
TOO OMe ea ah Waa mene vere Oi ee as, eae TESTO VASES oo a ie ela 51.6 16 
OO 2! RN ER ESL: Oe ae LOBED AC PT Pala eh be 39.0 41 
DAC See ie eevee vee Ee eT eS IGS) 4 esa A eee A a Nc elt FEY 42.0 0 
1 Sixty-four tests of individual cones were made, from which the series given in 
Table 8 is Selected to Show the effect of the range of temperature from below the 
ignition point of Dcuglas-fir wood to a point higher than that ordinarily reached in 
slash fires or fires that have air drafts mixed through flame, as do forest fires. 
While a crown fire is traveling the flame remains in a single 
crown from about 15 seconds to a minute, with a temperature of 900° 
to 1,100° F. 
60634— 24 3 
The ignition point of Douglas-fir needles is 650° F., 
