240 FIELD CROP PRODUCTION 



of plants to a butterfly, the Latin name of which is 

 papilio. The plants of this sub-family are divided into 

 several genera, about a dozen of which contain the im- 

 portant agricultural species. In the older use of the term 

 " legume " it included all of the members of the Legumi- 

 nosae, but it is now frequently used in agricultural litera- 

 ture as including only the cultivated members of Papil- 

 ionacese. While the members of Papilionacese vary 

 greatly in size, shape of their parts, and in their manner 

 of growth, they have several features in common that 

 distinguish them from the grasses and other families 

 containing agricultural plants. Unlike the grasses, they 

 have a tap root which varies in depth of growth and man- 

 ner of branching. In some species, as in the white clover, 

 the stoloniferous habit is more or less strongly developed, 

 while in others, as the pea or bean, no stolons are present. 

 The leaves consist of three or more leaflets carried on a 

 leaf-stalk or petiole with stipules or leafy outgrowths at 

 its base, the size and shape of the stipules being a feature of 

 importance for the identification of many species. As in 

 the grasses, the leaves are arranged alternately and spirally 

 on the stem and branches. 



241. The flowers are one of the characteristic features 

 of the Papilionacese, and, as was pointed out, bear a 

 fancied resemblance to a butterfly. The flowers are 

 made up of calyx, corolla, stamens, and pistil. The corolla 

 is made up of five petals which are unequal in size. The 

 largest and most conspicuous one is called the standard. 

 The two that grow out laterally, one from each side, are 

 at more or less right angles to the standard, and are 

 known as the wings. The other two are more or less 

 coherent along one margin and form a boat-shaped struc- 

 ture called the "keel," in which the stamens and pistil 



