14 HORTICULTURAL MANUAL. 



shoot, known as the plumule, starts. All seeds start the 

 root or hypocotyl downward prior to the starting of the 

 plumule upward to be exposed to the air and sun. 



Germination is said to be completed when the young 

 plantlet forms perfect leaves and is capable of living with- 

 out additional support from the stored nutriment in the 

 seed. 



16. Some of the Modes of Root-growth. As the hypo- 

 cotyl, or first seed-growth, extends downward into the soil, 

 rootlets start from its sides and rounded point. From the 

 point the main or tap-root extends downward, and from 

 the sides extend the branch or feeding roots. The length 

 of the hypocotyl varies in seeds of different plants and 

 trees. The long list of plants that lift up bodily the 

 halves of the seed or what remains of it, such as the bean, 

 pumpkin, and most of the fruits, make a relatively long 

 growth of the hypocotyl during the process of root-exten- 

 sion. This seems to be a wise provision for forming a 

 foundation for the forcing process of lifting the bulk} 

 cotyledons to the surface with a force that often uplifts a 

 hard-baked earth surface. 



This class of seeds should be planted shallow. If as 

 deeply planted as peas, they will not be able to force the 

 cotyledons to the surface. At the West a heavy rain fol- 

 lowed by dry days often forms a crust that makes it diffi- 

 cult for apple-seed to germinate if planted more than three 

 fourths of an inch deep. If the soil is well firmed in 

 planting, the whole of this numerous class will do best if 

 not covered more than from one half to three fourths of 

 an inch deep (Fig. 1). 



On the other hand, all plants that do not lift up the 

 seed-leaves or cotyledons will bear deeper planting. The 

 pea is an example. This forms the two cotyledons, but 

 they remain in the soil and the slender shoot pushes up 



