8 
Colorado Experiment Station 
The cleaning of seed can be done during the winter days when 
there is a let-up in farm work, and before the rush of spring work 
begins. 
The Germination of the Seed. —The seed contains the germ or 
young plant, often surrounded by stored food material. This stored 
material will be used to nourish the young plant until it secures a 
foothold in the ground and is able to absorb water and has sent out 
leaves which enable it to make its own food. 
Certain conditions are necessary for the germination of all 
seeds. These are as follows: (1) Water, (2) moderately high tem¬ 
perature, and (3) air (oxygen). If any one of these is lacking, the 
seeds will not germinate. 
Hard Seeds. —Most grains have seed coats which permit the 
ready intake of water. It very often happens that the seeds of alfal¬ 
fa, sweet clover and other legumes have seed coats which are almost 
impermeable to water. Such seeds are called “hard seeds.” They will 
not grow readily when placed under perfect conditions for germina¬ 
tion. Hard seeds are not necessarily poor seeds. Some of them will 
germinate in several weeks; some will remain in the ground for an 
indefinite period without germinating. It has been determined ex¬ 
perimentally that on the average about one-third of the hard seeds 
will germinate in a reasonable time. Unhulled sweet clover seed may 
often have as much as 85% hard seed. Hulled sweet clover has a 
lower percentage of hard seed than the unhulled. Alfalfa seed will 
often have 20% to 25% hard seed. 
It is claimed that a larger percentage of hard seeds is pro¬ 
duced in dry climates or when ripening takes place under dry sea¬ 
sonal conditions than in moist climates or moist seasons. 
The permeability of leguminous seeds can be increased by “scari¬ 
fying”; that is, passing them through a machine that scratches the 
surface. The ordinary alfalfa huller is effective for this purpose, 
as is shown by the experiments of Harrington, who found that al¬ 
falfa grown under a variety of soil and climatic conditions had about 
90% of hard seeds if hulled by hand, and only about 20% if hulled 
by machine. 
Scarifying machines are on the market. One machine, known 
as the Ames Hulling and Scarifying Machine, which may be operated 
with a one-horse power motor, or a two-liorse power gasoline engine, 
has a capacity of from 18 to 25 bushels of alfalfa or sweet clover 
seed an hour. Scarifying, or abrasion of the seed surface, is ac¬ 
complished by blowing the seed over garnet paper. The Ohio Agri¬ 
cultural Experiment Station gives the following results from using 
this machine, with sweet clover seed: 
Seed not scarified.30% germination 
Seed scarified .87.6% germination 
It is unwise to plant leguminous seeds with a high percentage 
of hard seed. 
