96 PAPILIONACEiE, 



mechanism of the Gorse and Broom, for here the staminal tube 

 is inclined to rise but is held down by the keel, and when an 

 insect presses with more than a certain weight on this, is 

 suddenly released and springing up sends out a cloud of pollen. 

 All these flowers require the visiting insect to be of some weight, 

 and do not waste their pollen on butterflies, but give it to bees. 

 On the other hand there are flowers, mostly of a red colour, in 

 which the release of the stamens is brought about quite easily 

 by a slender proboscis separating the knobs on the wings or 

 keel which hold the stamens down. Such flowers offer honey 

 to their visitors and are adapted for butterflies. These are only 

 the broad outlines. Individual flowers differ in details, and 

 these are well worth investigation. Much may be done by 

 simple experiments with pressing the keel down, or inserting a 

 bristle ; but for the really conclusive observations one must 

 watch insects at work on the flowers. The lateral facing of the 

 flower ; its blaze of yellow for bees, or red for butterflies, 

 so that the right insect may easily find it ; and the little details 

 of anthers, keel, and wings, must all be regarded as designed 

 for the one end of cross-pollination : and the precision with 

 which a flower will open to the insect and close again after 

 planting pollen on that part of its body which will come in 

 contact with the stigma of an older flower, shows how well 

 every part is adapted to its purpose. 



KEY TO THE GENERA. 



JVery spiny green shrub without flat leaves . p. 97. ulex. 

 ^ \ Leafy plants b 



b 



J Anthers alternately long pointed or short rounded . . c 



\ Anthers all similar . . d 



J Leaves all simple ; pod inflated . . /. 99- crotalaria. 



^ \Stem green, angular ; leaves small or absent. /. 98. cytisus. 

 r Leaves at least the lower of three leaflets ..... e 



d-| Leaves odd-pinnate, flowers blue, mauve or pink. . . e 

 [ Leaves pinnate ending in a branched tendril, p. 117. vicia. 

 J Stalks of leaflets all equal f 



^ \ Stalk of middle leaflet distinctly longer than the others, i 

 \ Leaflets notched or heart-shaped, finely toothed ; tender 



{\ herbs with creeping stem ......... g 



y Leaflets not toothed — erect or difl"use plants . . . . h 



\ Flowers blue and white, solitary or in pairs on slender 



g^ stalks ......... p- III. PAROCHETUS. 



[ Flowers in heads, yellow, white or pinkish/, no. trifolium. 



