1676 



A TEXTBOOK OF THEORETICAL BOTANY 



A. precatorius has hard, red seeds with black tips which are often manu- 

 factured into necklaces. In India they are used as weights. The roots 

 yield Indian liquorice. 



In this sub-family the pollination is again somewhat different and 

 depends upon a brush mechanism. In Vicia cracca (Fig. 1533) the wing 

 petals are united to the keel at two places. When a bee visits the flower it 

 settles on the wings and since these are firmly united with the keel they act 



Fig. 1533. — Vicia cracca. A, Flower 

 from above after removal of 

 standard and calyx. Vicia 

 sepium. B, Androecium and 

 style in position in the unopened 

 flower. {After Kniith.) 



as the arms of a lever and cause its depression. When the flowers have 

 reached about half their full size the anthers dehisce. They closely sur- 

 round the style, the upper part of which is beset with upwardly projecting, 

 dense, fine hairs. Thus the stigma and the hairs become liberally dusted 

 with pollen. When a bee visits the flower, pollen adheres to its underside 

 and the stigma is, at the same time, rendered sticky and receptive by the 

 brushing of its papillate surface. 



In many species of this genus there are extra-floral nectaries. These 

 are dark-coloured spots situated on the underside of the stipules. They 

 only secrete nectar in sunny weather. The secretion is sought after by ants, 

 which may perhaps protect the plants against caterpillar attacks. 



The genus Lathyrus is a large and irnportant one. There are over 

 100 species. Lathyrus odoratus is the species ffom which the garden Sweet 

 Peas have orginated. L. latifoHus is the Everlasting Pea. Several species 

 are of economic importance. L. sativiis and L. cicera are used as fodder, 

 while L. macrorrhizus has tuberous roots which may be eaten like potatoes. 

 Morphologically the genus is interesting because of the large green stipules, 

 which in L. aphaca are the only assimilating organs. The lamina of the leaf 

 is converted into a tendril, while the petiole may become flattened into a 

 phyllode, as in L. nissolia. 



