490 THE STRUCTURE OF ECONOMIC PLANTS 



germination, this becomes mucilaginous and is absorbed by the 

 cotyledons. 



Development of the Seedling. — Under greenhouse condi- 

 tions, scarified seeds germinate rapidly.^ The primary root 

 emerges by the end of the first or second day, and subsequently 

 there is a rapid elongation of the axis so that it may reach a length 



Fig. 151. Stages in development of seedling; A, three days; B, five days; C, seven days; 



D, three weeks ; E, first foliage leaf. 



of i or 3 inches by the third or fourth day. There is an early 

 differentiation of lateral roots, and by the fifth day, small branch 

 roots can be seen at the upper root level. The hypocotyl elongates, 

 carrying the cotyledons forward with it; and as they emerge 

 from the soil and are liberated from the seed coat, the elongation 

 of the cotyledonary petioles separates them from each other. The 

 cotyledons are deeply bilobed, the lobes being obtuse or subacute, 

 and the rounded auricles are rather prominent. Following the 



' The seedling studies described in this section are based upon material grown from seed 

 supplied by the Director of the Virgin Islands Experiment Station. 



