16 PRINCIPLES OF PLANT CULTURE 



allowed to become dry, the seed-case does not readily 

 transmit water at growing temperatures. Such seeds may 

 lie for weeks, and even months, in tepid water without 

 swelling, but when the water is heated to a certain degree, 

 they swell promptly, a fact often turned to account by 

 nurserymen (36). We cannot always judge by the ap- 

 pearance of a seed-case whether it will transmit water 

 readily or not. 



The term seed-case is here used to designate the outer 

 covering of the seed as the word seed is understood by 

 the seedsman or planter. Every seed, as we buy it in 

 the market, or when ready for planting, has one or more 

 covering layers. In the peanut, for example, what we here 

 call the seed-case is commonly called the shuck; in the 

 cocoanut it is called the shell; in the bean and Indian 

 corn it is more often called the skin. In botany, the outer 

 coverings of seeds are given different names, as pericarp, 

 testa, etc., according to their exact office in the make-up 

 of the plant. To avoid explaining the technicalities of a 

 complex subject, it seems preferable to adopt a term that 

 will include the various words used in botany to designate 

 the outer coverings of seeds. 



The nature of the seed content and the salts in the 

 soil also influence the rate of absorption of moisture. 



GERMINATION 



28. What is germination ? If we place a few viable 

 grains of Indian corn between the moist cloths of a seed- 

 tester (Fig. 6), cover with the glass and place in a warm 

 room, we shall observe, if we examine the corn frequently, 

 that a change, aside from the swelling, will soon take place 

 in at least a part of the grains. A viable seed is one that is 



