68 SEEDS AND FRUITS 



In most cases the resting stage is brought about by the drying 

 out that follows ahnost immediately after seeds attain their 

 full size. In drying out many seeds lose from one-half to two- 

 thirds of their green weight. For example, after Clover seeds 

 attain full size both pods and seeds begin to dry and within three 

 or four days the seeds lose sixty per cent or more of their green 

 weight. With the loss of so much water, naturally the Kfe 

 processes are much checked; for the life processes are so de- 

 pendant upon water, that they are checked unless there is plenty 

 of water present. Some investigators have held that the life 

 processes actually stop but they never stop as long as seeds can 

 germinate. They are going on but very slowly. 



The dried out condition of resting seeds apparently does not 

 impair their vitality unless too much prolonged', but enables 

 them to endure extreme conditions. In the active condition the 

 embryos of most seeds are killed by a temperature a little below 

 freezing, but seeds of vUfalfa, Mustard, and Wheat in the resting 

 state have been kept for three days in a temperature of —250° C. 

 and afterwards successfully germinated. A temperature of 60' C. 

 kUls most seeds when active, but, if in the resting stage and kept 

 dry, many seeds can endure a temperature of 100° C, that of 

 boiUng water, without injury. 



The length of the resting period varies much for different kinds 

 of seeds and for seeds of the same kind. In a sample of Clover 

 seed, for example, many of the seeds may germinate in two or 

 three days, and some may not germinate for a month or a year. 

 Although the seeds of some wild plants will germinate as soon as 

 mature, if given favorable conditions of moisture and warmth, 

 most of them, however, have a rest period which extends over 

 days, weeks, months, or even years, and often saves the young 

 plants from getting started at a time when they would soon be 

 caught by unfavorable conditions. Excepting some seeds like 

 those of the Clovers and Alfalfa, the seeds of cultivated plants will 

 usually germinate about as soon as mature. Although a desirable 

 feature, it sometimes results in loss, in that Corn, Wheat, Oats 

 and other crops germinate in the field if the weather following 

 harvest is warm and wet. The resting period, which is retained 

 by Wild Oats and some other wild plants kindred to cultivated 

 ones, has been lost from our cultivated plants through many 

 years of selection. 



