EEFORESTATIOH OH THE HATIONAL POEESTS. 
15 
angle and a hole cut in the lower end, the seed will gradually work 
out with the wings broken off. 
Still other methods depend wholly on the use of screens. The sim- 
plest of these is to rub the seed as it comes from the extractor over a 
fine screen fastened on an empty box or stout frame. The rubbing 
may be done with a stiff scrubbing brush, a block of wood covered 
with corrugated rubber, a piece of tough carpet, or the hands covered 
with rough gloves. As the wings are rubbed off the seeds gradually 
drop through the screen, leaving a large part of the wings and all 
of the coarser impurities on top. One-sixth inch mesh is the best size 
for screening yellow pine and Douglas fir seed; for lodgepole pine 
and Engelmann spruce one-eighth inch mesh is preferable. The 
wings are more easily removed if the seed ai*e moistened slightly with 
cold water before screening. 
The first screening ordinarily does not remove the wings com- 
pletely. To get rid of what is left, the 'seed and small chaff coming 
through the first screen may be churned, together with several small 
pieces of wood, in a small, cylindrical drum, covered with very fine- 
meshed wire. This removes the rest of the wings, which with other 
small particles of dirt, fall through the screening, leaving clean seed 
behind. 
A somewhat similar method, preferable when the work is done on 
a large scale, makes use of a mechanical cleaner or wing crusher. 
This consists of a rotating cylinder bearing upon the outside several 
scrubbing brushes with stiff bristles, which, during about one-third 
of each revolution, press firmly against a wire screen of mesh fine 
enough so that the seed itself will not pass through it. The screen 
against which the brushes press as they revolve may be adjusted to 
regulate the pressure of the bristles against it. The seed is dropped 
into tlie space between the screen and the brushes, and the wings are 
removed as they pass under the brushes ; the fragments of wings and 
chaff drop through the wire screen. When using such an apparatus 
with pine seed, a slight moistening of the seed with cold water is ad- 
visable before putting them intO' the hopper. 
A device designed by Forest Ranger William Kerlee of the Bitter- 
root National Forest is both rapid and effective with western yellow 
pine. It consists of a rectangular churn 2 feet by 2 feet by 7 feet 8 
inches. Longitudinally placed through its center there is a cylinder 
which is revolved in one direction by means of a belt. Upon this 
cylinder the churn itself is revolved in the opposite direction. From 
two opposite inner surfaces of the churn, wooden teeth project to- 
ward the cylinder, and on the cylinder similar wooden teeth project 
toward the periphery of the churn. The two sets of teeth overlap by 
several inches and clear each other by from one*fourth to one-half 
