318 WALDRON— THE PEANUT 



simulating typical root hairs. (2) a growth in thickness occurs by 

 a process similar to that of periderm formation, by which the diam- 

 eter of the subterranean part is somewhat increased. Pettit notes 

 another difference in the absence of what she calls plasmolytic cells 

 situated in the center of the cortex of the epigeal part. These cells 

 have not been observed by the author. 



The absorptive hairs (Plate LXXIX, Fig. 7) are large, unbranched, 

 one celled and average nearly a millimeter in length. Each is 

 slightly enlarged at the base which represents the size of the original 

 cell from which it springs. No stomata were seen, but lenticels 

 were present which developed into a white proliferation of cells 

 when exposed to a moist atmosphere as did some of those of the 

 epigeal portion. 



The examination of a cross section of this hypogeal area showed 

 the outer layer of the cortex dividing into two to four layers of cork- 

 like cells. The cells of this sub-epidermal layer are somewhat larger 

 than those of the rest of the cortex. Although these apparent phel- 

 logen derived cells have tbe appearance of periderm, according to 

 Pettit, they are free from suberin, as would be expected from the 

 presence of absorption hairs on their exterior. 



Anatomy of the Yoimg Fruit. As noted above (see page 316) the 

 ovary, situated at the tip of the gynophore remains inactive until 

 the time comes for fruit maturation. The epidermis at this time 

 is composed of much deeper and narrower cells radially, than that 

 of the non-hairy part of the gynophore. They become deep, tap- 

 ering and lignified at the tip forming a hard, but not capped apex. 

 The lumen of those at the tip contain numerous granules that are 

 not evident further back and suggest a relation to the geotropic 

 reaction of the gynophore. Three or four hypodermal layers, that 

 later form the outer mesocarp, are composed of markedly cylindric 

 cells. A branching bundle system within this is a continuation of 

 that of the gynophore which gradually disappears toward the tip. 

 Just interior to this are a few layers which later assume marked 

 appearance and importance as tissue which becomes gradually lig- 

 nified to form the strengthening inner shell layer of the fruit. The 

 innermost tissue next to the ovarian cavity is composed of several 

 layers of tiny nearly square cells arranged in radiating rows. 



Anato7ny of the Developing Fruit. When the ovary begins to en- 

 large, the epidermal cells elongate longitudinally and later become 

 ruptured. This epidermis with the subjacent layer, is rubbed or 



