EXTRACTING AND CLEANING FOREST TREE SEED. 15 
temperature the quicker the drying can be accomplished. Dry heat, 
however, is more effective than moist heat, and heat that is too in- 
tense is very apt to impair the fertility of the seed. This is particu- 
larly true of intense moist heat. Often this injury to seed is not 
appreciated at the time, since the deterioration does not become 
apparent until several months later. : 
The maximum temperature which should ordinarily be applied to 
all species except lodgepole pine is 120° F. This can be raised safely 
to 130° F. if the air is dry and good ventilation provided. Lodge- 
pole cones should not as a rule be subjected to a temperature of more 
than 140° F., although this can be raised safely to 150° F. under 
favorable conditions. Lodgepole pine cones are hardest to open; 
then come in order western white pine, western yellow pine, Engel- 
mann spruce, and finally Douglas fir, which can often be dried satis- 
factorily at a temperature of 110° F. 
TIME REQUIRED. 
At well-equipped plants lodgepole pine cones should be thoroughly 
dried at a constant temperature of 140° F. in from 8 to 10 hours, and 
other species at a constant temperature of 120° F. in 10 to 15 hours, 
assuming that the cones are mature and moderately dry when put 
into the kiln and that the room is evenly heated and well ventilated. 
Under less favorable conditions these periods may be greatly in- 
creased. In one instance, lodgepole pine cones dried in a tent at 
140° F. took 44 hours to open. The difference was due mainly to 
loss of heat in the tent and its uneven distribution. Preliminary 
drying of the cones for a few hours at 80° to 100° F. has been found 
an advantage. Opening will also be hastened if the cones are spread 
thinly in the trays and stirred frequently, to make the drying more 
uniform. 
EXTRACTING SEED FROM DRIED CONES. 
After the cones have been thoroughly dried, the next step is to 
extract the seed. Merely to rake over the cones as they are drying 
in the sun or kiln is the simplest but least efficient method. It is 
most successful with western yellow pine, but even with this species 
better results can usually be obtained by shaking. The practice of 
placing cones in sacks and beating them with clubs to loosen the seed 
has also proved unsatisfactory. It requires too much time and yields 
only a little additional seed, which is apt to be of poor quality. 
TRAY SHAKERS. 
In nearly every case, therefore, to secure the maximum amount of 
seed some method of shaking must be used to release the seeds from 
the opened cones. One of the earliest and simplest devices is a tray 
