40 BULLETIN 234, U. S. DEPARTMENT OF AGRICULTURE. 
Lodgepole-pine seed is hard to extract from the cones, and a drying 
temperature of from 140° to 150° F. is necessary before the latter will 
open satisfactorily. During the process of drying there must, of 
course, be enough air circulation to remove the moisture given off by 
the cones. Where only a few hundred bushels of cones are to be han- 
dled, any small room, provided it can be made tight, will serve as a 
dry kiln. Trays with wire-mesh bottoms, on which the cones are 
spread in a single layer, should be arranged in tiers, so as fully to utilize 
the available space. Eight hours of drying at a temperature of from 
140° to 150° should open the cones to the extent necessary. Hourly 
thermometer readings should be taken, in order to insure that the 
proper temperature is maintained. One higher than 150° may 
injure the seed, while one lower than 140° will not open the cones. 
Provision must also be made for removing the moist air from the 
kiln. The latter should be run continuously day and night, since 
if it is operated intermittently the cost of extraction will be increased. 
Wherever the cones can be stored in bins with a free circulation of 
air, it is usually best to defer seed extraction until late in the winter. 
After two or three months in such bins the cones will have lost a 
large percentage of moisture merely through natural air drying. 
After the cones have been opened in the drying kiln they must be 
shaken or thrashed out in order to extract the seed. This is done by 
means of a cone shaker, which consists merely of a revolving box or 
drum with a wire covering, through which the extracted seeds fall to 
the ground. The wings can then be removed by sacking the seed 
loosely and giving it a vigorous kneading. Where a large quantity 
of seed is handled a cheaper method is to moisten it slightly and rub 
it through a wire screen with an ordinary scrubbing brush. After 
being freed of their wings the seeds are dried again. The cleaning of 
the seed is finally completed either by winnowing it or by running it 
through a fanning mill fitted with screens of proper mesh in order to 
remove all foreign matter, such as pine needles, cone scales, broken 
wings, and dirt. 
It is usually cheaper to extract and clean seed in the immediate 
vicinity of the area where the cones are gathered than to transport 
quantities of the bulky cones to a central seed-extraction plant. 
When seed is to be cleaned regularly in large quantities, however, 
specially constructed drying kilns are best and cheapest in the long 
run. A number of such permanent seed-extraction plants have been 
constructed on the National Forests. These include several small 
plants, with a capacity of about 90 bushels of cones per 24-hour 
running, and one large plant capable of handling about 200 bushels 
in 24 hours. In the latter, located on the Medicine Bow National 
Forest, a hot-air blast is forced through a large, slowly revolving 
cylinder, so that the cones are dried and the seed extracted at the 
