MORPHOLOGY, GENETICS AND BREEDING 53 



Pod 



When the peg reaches its maximum penetration of the soil it loses its 



geotropism and the tip turns to a horizontal position. At the same time 



the pod begins to enlarge and development rapidly ensues. Enlargement 



of the pod proceeds from base to apex (figure 15). Early stages resemble 



Figure IS. — Successive stages in the development of a peanut fruit. Left to right : an 

 ovary at time of fertilization ; young aerial peg ; elongated peg after soil pene- 

 tration ; the tip of the peg turned to a horizontal position and the beginning of 

 pod enlargement; early immature stage of pod development; mature fruit. 

 (after Smith, 66.) 



one-seeded pods in appearance. The more rapid development of the basal 

 segment is associated with the earlier development of the basal seed. 

 When the apical seed aborts, as occurs frequently, enlargement of the 

 apical portion proceeds no further. 



At maturity, the shell is usually reticulate and more or less constricted 

 between the seeds. According to Thompson (72) and Russell (63) the 

 superficial exocarp layers flake oflf during development. The character- 

 istic reticulations underlying the veins are ridges of mechanical tissue 

 arising as outward extensions of the sclerenchymatous mesocarp layer. 

 This layer is continuous except at the sutures. The endocarp consists of 

 a parenchymatous tissue which surrounds the ovules during development. 

 The cells of the endocarp lose their contents and their walls collapse as 

 the pod matures. 



The peanut fruit is a one-loculed, structurally dehiscent, but func- 



