Cleaned, Treated and Tested Seed 
15 
the Colorado Seed Laboratory lias prepared a collection of the most 
common weed seeds* (Fig. 4). By means of this collection the farmer 
can easily distinguish seeds of the common weeds. 
After the separation or purity test is complete the resulting divi¬ 
sions will consist of pure seed in one pile, dirt, chaff and broken seed 
or other inert matter in the second pile, and weed seeds or other seeds 
in the third. The percentage of purity can be accurately determined 
when scales are available or roughly estimated if there are no scales 
to be had. Unknown seeds which do not occur in the authentic collec¬ 
tion may be sent to the Colorado Seed Laboratory for identification. 
Fig. 3.—Showing method of dividing original purity sample in order to obtain the 
proper amount for purity analysis. This method of dividing eliminates 
any tendency of the individiial to select either good or bad seed for 
analysis. 
Much has been written regarding home purity tests, but there is 
still much doubt as to the accuracy of such tests even when good scales 
are obtainable. There is oftentimes marked variation in purity tests 
made by experts using highly specialized apparatus, so it is obvious 
that a rough estimate or the use of even an ordinary scale would mean 
wide variation—far greater than the usual 2% allowed in the seed 
laws of the several states. Emphasis should be placed upon the ability 
of the Seed Laboratory to give the farmer that which he cannot af¬ 
ford to obtain for himself—the knowledge of highly trained experts 
and the use of specialized apparatus, which make for accuracy 
Germination Tests. —Germination tests can be made by anyone, 
if the correct method is followed and care is exercised. For germina¬ 
tion, all seeds require heat, air and moisture. 
It has been found after many years of experiment that different 
crop seeds require different seed bed conditions for the most accurate 
*Each collection case contains 24 clitferent weed seeds and may be pur¬ 
chased from the Seed Laboratory at the cost of preparing—75c. 
