10 EXTRACTING AND CLEANING FOREST TREE SEED. 
sufficient room for expansion, however, it is safer, in planning on 
the number of drying sheets needed, to allow only 8 or 9 bushels to 
each sheet. 
Time required.—The time required for cones to open varies greatly 
with climatic conditions and slightly with different species. A suc- 
cession of clear, sunny days and frosty nights, with good winds, will 
open cones very rapidly. In good weather mature yellow pine cones 
will open in from 3 to 5 days. Under ordinary weather conditions 
from 4 to 10 days are required, and in damp, stormy weather often. 
as many as 15 days. Douglas fir and Engelmann spruce usually 
require a day or two longer under the same conditions. Lodgepole 
pine takes so much longer that sun drying is seldom attempted. 
Cones picked early in the season, before they are thoroughly ripe, 
open much more slowly than those picked later. | 
Number of sheets needed—An estimate of the number of drying 
sheets needed for 1,000 bushels of western yellow pine cones may 
be made as follows: Ten bushels of cones can be spread on each 
sheet; if it takes 5 days to open each batch of cones and there are 20 
good drying days in the fall each sheet can be used four times. In 
other words, 40 bushels can be handled on each sheet. Dividing 1,000 
by this gives 25, the total number of sheets needed for the work. 
Bad weather or the need of additional sheets for covers may make 
this number insufficient. It is always well, therefore, to make the 
estimate liberal, since lack of a few drying sheets at a critical time 
may cause serious delay and even the loss of much seed. 
DRYING CONES BY ARTIFICIAL HEAT. 
With lodgepole pine, and with other species when weather condi- 
tions are unfavorable, artificial drying must be used. This method 
is quicker than drying by natural heat and is not dependent upon 
the weather. It is, however, more difficult, more expensive, and 
ordinarily does not yield as good seed; therefore it should not be 
used except when outdoor drying is not practicable. Most of the 
artificial drying is done at permanent, fully equipped extracting 
plants to which cones are shipped from a large area. This circular 
is designed for the smaller, temporary plants which must be handled 
by less experienced men with simple applhances. 
EQUIPMENT NEEDED. 
Cabins.—The first essential in drying by artificial heat is some sort 
of shelter which will protect the cones from weather and be sufh- 
ciently tight to make it possible to raise the temperature to at least 
110° F. An empty room in a cabin may serve the purpose and often 
makes as satisfactory a substitute for a regular kiln as can be ob- 
tained. It must have tight walls and plenty of space for trays 
around the sides and for a stove. Often one room of a cabin is used 
for drying and another for storing and extracting. 
