THE DICOTYLEDONES 



1677 



The Phaseoloideae are another large sub-family, comprising some fifty 

 genera which are widely distributed in the tropics and warmer parts of the 

 world. The most important genus is Phaseolus with 160 species, mostly 

 in tropical regions; P. miiltiflorus (Scarlet Runner) and P. vulgaris (Kidney 

 or French Bean) are both South American in origin and were originally 

 cultivated for their flowers. Another extremely important species is Glycine 

 soja which provides the Soya Bean of commerce (Fig. 1534). Not only is the 

 bean itself used for food but the pressed seeds provide an oil which after 



Fig. 1534. — Glycine soja. Soya Bean. Shoot 

 with pods. 



fractional distillation can be used, not only for nourishment, but also as an 

 illuminant. The flour is used as cattle cake and the foliage as fodder. A 

 fermented mash of the seed provides the aromatic "Soy" which is the 

 base of Worcester sauce. Another tropical genus which is extensively 

 cultivated is Dolichos. D. lablab is grown for its edible seeds, while D. 

 hiflorus is used for feeding horses and cattle, particularly in India. A number 

 of genera are grown as ornamental flowers, for example Ketmedya. The 

 genus Physostigma includes two African species, of which the poisonous 

 P. venenosum is the Calabar Bean, which is used in various ordeal cere- 

 monies. 



The pollination mechanism in this sub-family may be exemplified by 

 Phaseolus (Fig. 1535). The flowers yield nectar and the anthers closely 

 surround the style and shed their pollen on to it, but the stigma is never 

 dusted. There are two nectar passages and the filament of the single free 

 stamen broadens out forwards so that it closes completely the staminal 



