PROCESSING SEED OF GRASSES AND OTHER PLANTS 3 
Preliminary trials with the hammer mill indicated that deawning 
of Canada wild-rye was only partly accomplished and that damage to 
the seed was high. Tests were then made to determine the effect of 
cylinder speed, rate of feeding, screen size, and number of times milled 
on deawning and damage to the seeds. It was apparent that proper 
adjustments of these four factors could be made to obtain a high per- 
centage of awn removal, little or no damage, and a product that could 
easily be seeded with ordinary farm machinery. The detailed data 
presented in table 2 for Canada wild-rye show the relation of speed 
of cylinder and rate of milling to the other factors in this table. Tests 
similar in detail were made with the other species studied but only 
averages for the optimum operation of the mill are given (table 3). 
Each lot of grass seed used in these studies was carefully examined 
before being processed to determine gross weight, test weight per 
bushel, number of seeds per pound, percentage deawned, percentage 
injured, percentage of purity, and percentage of germination. Test 
weight per bushel was determined from 3 aliquot samples by the use 
of a Boerner sampler in the usual manner. This may not be entirely 
accurate for grass seed, but since the same procedure was used 
throughout the studies, the tests of all the grasses are comparable. 
The number of seeds per pound was determined by averaging the 
number of seeds in 4 aliquot samples. The samples of the several 
species ranged from 2 to 8 grams. The percentage of seed deawned 
was determined by separating lots of 100 seeds, each taken from 3 
aliquot samples, into awned and deawned fractions. Three lots of 
100 seeds each were examined under the microscope, with a magni- 
fication of 10 to 20 diameters, to ascertain injury caused by threshing. 
Purity and germination tests were made according to standard pro- 
cedure in seed laboratories; the percentage of purity was obtamed 
from 1 aliquot sample of standard size and germination from 4 sam- 
ples of 100 seeds each. The expression of purity and germination 
in one figure in terms of percentage of live pure seed was adopted 
because this criterion is commonly used in trade channels and hence 
has the advantage of practicability. 
After the seed was milled to remove the awns from grass and 
the appendages from alfileria and virgins-bower, it was cleaned with a 
Clipper cleaner, model 16, to remove inert matter consisting chiefly of 
awns, straw, chaff, and cracked and ground seed. The tests made on 
the original seed were then made on the processed seed. By comparing 
the two sets of tests the effect of the methods used in milling can be 
determined. 
Accurate data on cost were recorded for all the trials. Labor was 
charged at 50 cents an hour, use of the mill and power at 23 cents, and 
use of the cleaner and power at Scents. These figures represent direct 
charges made at the nursery and are based on data accumulated for 
cost accounting. Milling and cleaning were computed separately. 
To each operation was added a charge of 30 percent for supervision 
and normal overhead. The total cost of both operations is presented 
as the cost of processing (table 3). 
