744 IOWA DEPARTMENT OF AGRICULTURE 



Examination of weed seeds. — The weed seeds should be examined for 

 kinds representing important weeds. A knowledge of what important 

 weed seeds are liable to occur in particular kinds of crop seed is very 

 helpful. For this reason the results of many tests are utilized in the 

 subsequent remarks on testing particular kinds of seed. Suspected weed 

 seeds should be carefully compared with the illustrations relating to this 

 class of seeds. Many kinds of weed seeds not illustrated in this bulletin 

 will be found. Most of these, as a rule, are of relatively minor import- 

 ance. 



The germination test. — It is important in separating pure seed for the 

 germination test that the counting be done indiscriminately — without se- 

 lection as to the appearance of the seed. The tendency of the beginner is 

 to select the more promising looking seeds for the germination test. It 

 must not be forgotten that the purpose of the test is to learn what per- 

 centage of the total pure seed will germinate. If the more promising 

 seed is selected, the results of the test are deciving in favor of the dealer. 



Of small seeds (such as forage crop and cereals), 200 are counted; 

 of larger seeds 100 are taken, each in duplicate. In the special individual 

 ear tests of corn only a few seeds are used. In adulterated samples the 

 necessary number of pure seeds can usually be obtained from the separa- 

 tion of the 1,000 seeds. It is obvious that accurate counting is important 

 to insure accuracy in computing the result. 



The conditions essential to seed germination are sufficient moisture, 

 warmth, and air. Sufficient water should be supplied to keep the seeds 

 thoroughly moisted during germination, but they should not be allowed 

 to rest in water. The temperature of living rooms ranging rfom 65° to 

 85° F. is suitable for germination. A place in the room should be se- 

 lected where the day and the night temperatures will be fairly uniform. 

 Thus the window sill is too cold in winter and a shelf directly over the 

 stove is too warm. The germination of some kinds of seeds is favored 

 by the varying day and night temperature of living rooms. Germinating 

 seeds must be supplied with fresh air. If the air is confined, it loses 

 its oxygen, which is necessary to germination, and there is no means for 

 escape of carbon dioxid, a gas produced by the germination process but 

 detrimental to it. A proper covering of cloth, paper, wood, or glass for 

 the seed germinator which prevents too rapid loss of moisture by evapora- 

 tion, while not hindering the admission of air, should not be neglected. 

 In order to insure sufficient air, very small seeds germinate best on top 

 of the germinator cloth or paper, while larger seeds do better when 

 placed between cloth or paper folds. 



When sand or soil is used in testing germination, the seeds should 

 have but a very light covering. Before the sprouts appear the surface 

 of the sand may be kept covered to hold the moisture. Germination in 

 sand and in soil is likely to be somewhat slower than when the test is 

 made in cloth or paper. 



Seed in the germinator should be examined daily to note the extent 

 and vigor of germination. Weak, slow germination indicates low vitality, 

 unpromising for good field results in plant production. 



