152 The Romance of Wild Flowers 
(M. sativa), because of its larger flowers, which can 
only be operated upon by humble-bees. The irrita- 
bility of this species is located in the staminal tube, 
and on this being excited by the bee’s tongue, the 
staminal tube and pistil are violently curled up to the 
standard, and the pollen showered over the bee, whilst 
the keel and wings become permanently depressed. 
Should no humble-bee arrive, the flower does not 
open, but self-fertilisation takes place. The pods of 
this genus are spirally coiled helix-fashion, but differ 
among themselves as to the number and closeness of 
the coils. Those of the Spotted Medick (JZ. maculata), 
which has been recommended as a fodder plant, are 
so sharp and so numerous that cattle often refuse to 
feed in the fields where they grow. The Melilots 
(Melilotus) have small honeyed drooping flowers in 
long racemes. Their general behaviour is much like 
that of Sain-foin. 
So far as we have gone we have seen great differ- 
ences in the flower-grouping of the Pea family, from 
the large distinct flowers of Broom, the loose racemes 
of Genista, the dense racemes of Sain-foin and Lucerne, 
the loose heads of Lotus, the denser heads of Kidney 
Vetch, until finally we reach the very compact heads 
of the Clovers (Trifoliwm). A novice who was 
confronted with a Clover-plant and a Pea both in full 
flower might well be pardoned for his failure to see 
a near relationship between the two. Yet if he is 
instructed to pull the head carefully to pieces and 
examine a single flower from the group, he will find 
in all essential points it is like that of the Pea, but 
the petals form a tube specially adapted to the long 
tongues of certain insects. Some of these flowers— 
