SEEDS AND SEEDLINGS 125 



fruits. Seeds may also be injured by extremes of temperature 

 and moisture in storage. The vitality of some of our important 

 seeds is indicated in the following table : 



Tomato 6 years 



Melon and pumpkin 5 years 



Beans and peas 4 to 5 years 



Mustards, cabbage and turnips 3 to 4 years 



Alfalfa 3 to 4 years ' 



Clover 2 to 3 years 



Corn, wheat, rye and barley 2 years 



Buckwheat 2 years 



Timothy 1 to 2 years 



Onions and celery 1 year 



Seed Testing. The fact that the vitality of the seed is in- 

 fluenced by so many factors makes it very important that seeds 

 used for growing of crops should be tested to determine their 

 power of germination. The national and state governments 

 maintain laboratories for this purpose, but any good grower can 

 make reasonably good tests for germination. A very convenient 

 germinator can be made as indicated in the laboratory exercises. 



Purity of Seeds. Commercial seeds sometimes contain con- 

 siderable quantity of weed seeds and other impurities. Analyses 

 to determine the amount of impurities are usually made in the 

 seed-testing laboratories and most states have laws controlling 

 the sale of commercial seeds. Some of the important field crop 

 seeds are shown in Fig. 88 and some of the most important weed 

 seeds in Fig. 89. 



LABORATORY EXERCISES. 



Exercise 1. Examine a good sized bean seed and note the hilum, 

 raphe and micropyle. Remove the seed coats and note the large cotyle- 

 dons, plumule and hypocotyl. 



Exercise 2. Germinate beans in wet moss so as to get long, straight 

 primary roots. When the roots are about three-quarters of an inch in 



