22 LAND DRAINAGE 



A soil constantly deficient in moisture is almost sure 

 to be deficient in all these useful nitrogen preparers, as 

 well as one which is over supplied with water. 



32. Moisture and germination. Water plays a very 

 important and interesting part in germination. Seeds 

 would lie indefinitely in a dry soil without germinating; 

 but where there is proper moisture, and correct condi- 

 tions of temperature and ventilation, the water makes its 

 way through the seed-coat and causes the seed to swell 

 till it bursts its coat. At the same time the presence of 

 the water in the seed promotes certain changes by which 

 the food stored in the seed is made ready for the use of 

 the young plant (more correctly called a plantlet or 

 embryo). (See Fig. 5.) It uses the food, begins to grow 

 out through the ruptured coat, and is soon established 

 in the soil. By the time, or even before, it has used up 

 the supply of food stored for it in the seed, it is ready to 

 use the food supply provided in the soil. 



33. Water the solvent and carrier. Before the 

 young plant can use the foods stored for it in the seed or 

 in the soil, the food must first be prepared and then 

 dissolved in the soil water. The water thus becomes the 

 carrier of the foods. The food-laden water may move 

 considerable distances through the soil to the roots. On 

 the other hand, when the soil is in proper physical condi- 

 tion, the roots develop remarkably, as was indicated in 

 paragraph 16. They reach out considerable distances, 

 and at the same time their branches become very 

 numerous, 1 so that there is not a cubic inch of soil for 

 some feet from the plant that is not penetrated or trav- 

 ersed by at least one root more usually by several. 



1 There are few of our common crops that fail to produce roots 

 as much as three feet in length, and some exceed ten feet. 



