46 THE PEANUT— THE UNPREDICTABLE LEGUME 



prostrate and the cuttings of its laterals not only flowered, but also con- 

 tinued to be prostrate, growing entirely in one direction from the original 

 point of root attachment. Clearly in this case, the polarity in development 

 which controlled the original lateral branch was maintained independently 

 in the excised portions. 



The stems of A. hypogaea are angular at first, containing a solid 

 pith which breaks down eventually so that old stems are hollow. The 

 angularity is also lost with age, the older branches becoming cylindrical. 

 There is no indication of woody development in the aerial portions of 

 Arachis. The genus consists exclusively of herbaceous perennials; pos- 

 sibly some forms of A. hypogaea should be considered annual. 



A variety of other growth forms are found among the wild species of 

 Arachis. Hoehne (34) described these briefly in his monograph but at- 

 tached little systematic importance to the variation present. The rhizo- 

 matous habit is clearly present in A. glabrata, for example, while several 

 of the species are stoloniferous, the stolons being partially buried at times. 



The pattern, order, and kinds of branching in the peanut are one of 

 the most interesting botanical features of the plant. Richter (59) gave a 

 brief description of branching orders wherein he let the central stem jixis 

 of the plant be an axis of the n order. Branches arising from the n order 

 axis were of m + i order and branches arising from n + 1 order axes 

 were n + 2 order, etc. Branches arising in the axils of the foliage leaves 

 were of two kinds, (1) vegetative and (2) reproductive. Since repro- 

 ductive branches normally do ,not give rise to further branching, their 

 production terminated all further orders of branching. For example, in 

 Richter's material, w + j order reproductive branches, by their specific 

 morphology, terminated the branching system. Prevot's (54) diagram 

 in his figure 10 shows a branching pattern similar to the type described 

 by Richter (59). We have observed branching systems of several varie- 

 ties of A. hypogaea and found that these differed widely not only in the 

 numbers of branching orders produced but also because they fell into 

 certain well defined patterns. 



Leaves 



Leaves of peanuts are usually pinnate with two pairs of leaflets. 

 Hoehne (34) reports that at least one species, and perhaps two are nor- 

 mally trifoliate. The leaflets may be elliptic-obovate, {A. hypogaea) , ellip- 

 tic-lanceolate, {A. glabrata) or almost linear {A. angustifolia) . The 

 leaflets may have inroUed margins or varying development of marginal 

 hairs. Hoehne (34) makes extensive use of these characters in his de- 

 scription of species. The leaves of the several species may be dark dull 



