26 ON FLOWERS AND INSECTS. [LECT. 



leaves a space through which the proboscis of the bee 

 can reach the honey, which is situated inside the tube 

 formed by the united stamens. In those Leguminosse 

 which have no honey, the stamens are all united to- 

 gether. Such flowers are, nevertheless, in spite of the 

 absence of honey, visited by insects for the sake of the 

 pollen. 



In other Leguminosse, as for instance in the Furze 

 (Ulex europceus), and the Broom (Sarothamnus scopa- 

 rius), the flower is in a state of tension, but the different 

 parts are, as it were, locked together. The action of the 

 bee, however, puts an end to this ; the flower explodes, 

 and thus dusts the bee with pollen. 



It would, however, take too long to refer to the 

 various interesting arrangements by which cross-fertili- 

 sation is secured in this great order of plants. 



It is impossible not to be struck by the marvellous 

 variety of contrivances found among flowers, and the 

 light thus thrown upon them, by the consideration 

 of their relations to insects ; but I must now call your 

 attention to certain very curious cases, in which the 

 same species has two or more kinds of flowers. Pro- 

 bably in all plants the flowers differ somewhat in size, 

 and I have already mentioned (ante, p. 1 3) some species 

 in which these differences have given rise to two distinct 

 classes of flowers, one large, and much visited by insects, 

 the other small, and comparatively neglected. In other 

 species, as, for instance, some of the violets, these differ- 

 ences are carried much further. The smaller flowers 

 have no smell or honey, the corolla is rudimentary, and, 

 in fact, an ordinary observer would not recognise them 

 as flowers at all. Such "cleistogamic " flowers, as they 



