II LEGUMINOSJd; 147 



bud, and usually the broadest ; the two lateral ones, 



called wings, are between the standard and the two 



lower ones, which are inside of all, and united more or 



less b}^ their outer edge into a single one called the 



keel, the claws of all five petals remaining free. 



Stamens, 1 ; the filaments in the British species 



either monadelphous, all united in a sheath round the 



ovary, or diadelphous, when the 



upper one is free and the other 



nine united in a sheath. Ovary 



single, one-celled, with one,, two, 



or more ovules arranged along 



the inner or upper angle (the one 



next the standard) of the cavity. '' ' 



Oj. 1 -1 T? -J. 1 Fig. 87. — Embry oof Bean. c,coty- 



btyle simple. Fruit a pod, ledon ; r, radicle ; .s plumule. 



usually opening in two valves. 



Seeds with two large cotyledons, and no albumen." 



It is probable that all flowers which have an 

 irregular corolla are fertilised by insects. The advan- 

 tage of the irregularity is that it tends to compel the 

 insects to visit the nectary in one particular manner, 

 and thus to fertilise the flower. In the present group 

 the result is that insects necessarily alight on a particular 

 part of the flower, when their weight in many cases 

 causes certain mechanical effects by which the pollen is 

 transferred to the body of the insect, and thus carried 

 from one flower to another. In the Leguminosse the 

 lower parts of the stamens coalesce into a hollow tube 

 (Fig. 99), the inner walls of which, at their base, secrete 

 honey in some species, though not in all. In the 

 former, one or more of the stamens is detached, as in 

 the Lotus (Fig. 100, a), or atrophied, so as to leave a 

 space through which bees can introduce their proboscis 

 into the tube. In those species which do not secrete 

 honey this is unnecessaxy, and the stamens are all fully 

 developed and united. 



The wings often present certain projections or bosses 

 which lock into corresponding depressions in the keel. 

 The result is that if a bee lights on and depresses the 



