MORPHOLOGY, GENETICS AND BREEDING 



39 



planting the hypocotyl length approaches a maximum of 10 to 12 cm. and 

 any further elongation necessary for emergence is made by the epicotyl. 

 This elongation of the epicotyl does not await attainment of mjiximum 

 hypocotyl length but appears to develop continuously in direct pro- 

 portion to depth of planting. It has likewise been observed that the length 

 of primary root varies inversely with planting depth to such an. extent 

 that peanuts germinating at their maximum depth for emergence are 

 almost devoid of roots. Bouffil illustrates this clearly in his photograph, 

 figure 1, page 10. At ordinary planting- depths the cotyledons (figure 7) 

 begin to shrivel (figure 8) as the foods leave them and go into the ex- 

 panding root and shoot systems. Twenty days after germination extreme 

 shrinkage (figure 9) is apparent. 



Figure 7. — Cotyledon from S-day old peanut seedling, cross section. The abundance 

 of stored food at this stage is revealed by the deeply stained cell contents, (ajter 

 Yarbrough,76.) 



