THE AWAKENING OF THE DORMANT SEED 435 



make out of apparently useless weeds, cultivated plants of great 

 value (Fig. 301). At present the milkweed plant is a pest to 

 farmers, springing up everywhere and crowding out better plants. 

 But it is thought that a valuable plant may be developed from 

 the weed, because on its seeds are fine hairs which may possibly 

 be strengthened and lengthened, and ultimately be made to rival 

 cotton and flax fibers. 



The awakening of the dormant seed. The seeds which 

 fall to the earth in autumn lie dormant until the first warm dayfc 

 of spring. Then they begin to grow; that is, they sprout and 

 germinate. The seeds which fall in the hot, dry, desert sands 

 lie dormant until a soft, gentle rain comes. Then under the 

 influence of warmth and moisture they rapidly develop into 

 tiny plants. Common observation teaches us that warmth and 

 moisture are necessary to awaken seeds and to start them in 

 their growth. If seeds are kept moist but lack heat, they rot 

 and are useless. The farmer who sows his crop in the early 

 spring dreads a cold " snap " because he knows that many of 

 his seeds will not develop for lack of warmth, but will rot in 

 the moist earth. Seeds do not all require the same amount 

 of warmth. Early pea, lettuce, and radish seeds develop in 

 fairly cold weather, because they require only a small amount of 

 warmth. Corn, squash, and onion seeds do not develop so early 

 in the spring, because they need more warmth. If you have a gar- 

 den, you know very well that you should plant some seeds as early 

 as March, others not until April, and still others not until May. 



Even in the warm summer days seeds do not develop if they 

 lack moisture. But after a warm rain tiny shoots are seen 

 springing up everywhere over the ground, the seeds from which 

 they came having been awakened into life and activity by 

 warmth and moisture. But although warmth and moisture 

 are necessary to awaken a seed to growth, they are not all that 

 is necessary because in addition to heat and moisture, there 



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