320 WALDRON— THE PEANUT 



mass of cells mentioned in connection with the maturing fruit. The 

 cells forming this are now remarkable in their shape, size, wall thick- 

 enings, and branches. (See Winton's article.) 



The structural relation of the carpellary wall to that of a leaf, 

 from which it is modified, is recognized, but with more difficulty 

 than that of many aerial leguminous fruits. By carefully splitting 

 open a fruit, as one ordinarily shells a peanut, it will be noted that 

 the seeds are attached to the somewhat convex side opposite that of 

 the beak. Thus the dorsal is recognized from the ventral suture. 

 Histologically these areas are not discernable in young ovaries, 

 except by noting the location of the ovule attachment, or that of 

 the style. This also locates exactly the position of the beak in 

 the mature fruit. In mature fruit shells there is a ventral suture 

 along which they quite readily split, due to a weaker, less lignified, 

 loose line of tissue as seen under the microscope. 



Concerning the exocarp, mesocarp and endocarp and their origin, 

 there is such a marked change and fusion of parts that any sharp 

 line of demarcation is impossible. The exocarp, which is typi- 

 cally derived from the lower leaf epidermis, is lost during fruit ma- 

 turation. The name endocarp, derived from the lower epidermis, 

 might be applied to the soft, internal tissue called inner parenchyma 

 by Winton. Practically the whole of the shell then would be the 

 mesocarp and can be subdivided into hypoderm, bundle area and 

 brs layer. 



The anatomy and cytology of the embryo not having been at- 

 tempted, that of the mature seed is also omitted. For details oj 

 the latter the reader is referred to Winton's article. 



Physiology 



Root Hairs 



To the writer, the thought suggested by others, as noted in the 

 histological discussion, that Arachis bore no root hairs, seemed con- 

 trary to expectation. The plant, with a semi-xerophytic tendency, 

 and growing well in a warm, loose soil, would be expected to have 

 them, at least when moisture is sufficient to stimulate their produc- 

 tion. 



Plants started in the greenhouse and carried on in flower pots 

 were therefore examined. Of twenty-five plants, one showed hairs 

 present near the tips of two of the young vigorous growing roots. 



