208 THE STOKY OP THE PLANTS. 



of its weak stem, and raise its leaves and flowers 

 to the air and the sunlight. 

 . At the base of every leaf, again, you will find, 

 if you look, two arrow-shaped appendages, which 

 block the way up the stem towards the deve- 

 loping flowers for useless creeping insects such 

 as steal the honey without assisting fertilisation. 

 On each appendage is a curious black spot, the 

 use or function of which is not apparent while 

 the blossoms are in the bud. But after a few 

 weeks' growth, the vetch begins to produce 

 solitary flowers in the angle of each upper 

 leaf ; flowers of the usual pea-blossom type, 

 but pink or reddish purple, and handsome or 

 attractive. These flowers contain abundant 

 honey to allure the proper fertilising insects. 

 Just as they open, however, the black spot on 

 the arrow-headed appendages of the lower 

 leaves, in whose angles there are no flowers, 

 begins also to secrete a little drop of honey. 



What is the use of this device? Well, if 

 you watch the vetch carefully, you will soon 

 see that ants, enticed by the smell of honey in 

 the opening flowers, crawl up the stem in hopes 

 of stealing it. But ants, as we knew, are 

 thieves, not fertilisers. As soon as they reach 

 the first black spot, they stop and lick up the 

 honey secreted by the gland, and then try to 

 pass on to the next appendage above it. But 

 the arrow-shaped barbs, turned back against the 

 stem, block their further progress ; and even if 

 they manage to squeeze themselves through with 

 an effort, they are met just above by another , 

 honey-gland and another barrier in the shape of 



