VITALITY OF SEED. 149 



474. The seeds of some plants continue good much 

 longer than those of others. Those of many wild plants, 

 for instance, will lie for many years without losing their 

 goodness, if they happen to be in such a place that they 

 cannot germinate, and afterwards when they have heat 

 and moisture, and other conditions necessary for germi 

 nation, they will produce plants. 



475. In digging wells, or in other deep excavations, 

 species of plants not before known in the place, often spring 

 up from the earth thrown out. These seeds must have 

 been lying in the earth many years, unable to grow 

 because the heat and air could not reach them. 



476. The seeds of the turnip, if kept in a dry, cool 

 place, continue good several years, and will germinate 

 nearly as well when five years old as when only one or 

 two. But the seeds of the grasses are comparatively 

 worthless when two years old, since few of them will then 

 germinate. Age, heat, moisture and fermentation, are 

 most injurious to seeds. 



477. Change of Seed. Most of our cultivated plants 

 originally grew wild, and in their natural state were much 

 less valuable than they now are. They have been brought 

 up to their present condition, and made far more useful 

 for the nourishment of men and animals, by careful 

 cultivation for many years. In all these plants there is a 

 natural tendency to lose what they have gained, and fall 

 back to their original condition. This can be prevented 

 in some degree by constant care in the selection of seed 

 and high cultivation ; but experience shows that in some 

 places these plants will gradually lose their best qualities, 

 however much care may be used to guard against it. 



478. To avoid the evils of sowing inferior seed, we may 

 use that produced in other localities, where special care 



