DIV. n SPERMATOPHYTA 555 



nected with the red stigmas of the early-flowering Hazel, and perhaps 

 also in the case of the cones of Coni ferae. Deeper investigation may 

 perhaps disclose further connections of this nature. 



The relation between flowers and insects depending on the sense of 

 form and scent of the latter remains unquestioned, and has been more fully 

 investigated for bees by v. FRISCH. What explanation of the strong 

 scent, increasing towards evening, of Lonicera, Philadelphia, etc., can be 

 given except that it serves as an attraction to night-flying insects, such 

 as Hawk-moths, which are led by the scent to find their food ? How 

 could the existence of nectaries and the excretion by the plant of an 

 important reserve food substance be accounted for, if the guests which 

 greedily consume it were not indispensable to the flowers'! How, 

 lastly, could the*construction of a dorsiventral flower, such as that of 

 Salci'i. or of Orchis, be understood if we did not relate it to the insects 

 which visit the flower in search of nectar, and in doing so effect pollina- 

 tion 1 The mutual adaptations between the form of flowers and the 

 bodies of insects are so numerous, and the experimental fact that plants 

 removed from their native country, though growing healthily, remain 

 sterile owing to the lack of the pollinating insects to which they are 

 adapted, is so well established, that no doubt can be entertained on the 

 mutual adaptations of flowers and insects. Usually the position of the 

 nectaries is such that the hairy body of the visiting insect must carry 

 away pollen from the flower ; often the pollen will be deposited on 

 special regions of the insect's body and, when another flower is visited, 

 will be deposited on the stigma. It is of importance that the pollen of 

 such entomophilous plants differs from that of the anemophilous 

 flowers described above. Pollen grains provided with spiny pro- 

 jections, or with a rough or sticky surface, are characteristic of 

 entomophilous plants ; the grains may remain united in tetrads or in 

 larger masses representing the contents of a whole pollen-sac (Orchis, 

 Asdepias). The pollen itself forms a valuable nitrogenous food for 

 some insects such as bees ; these form " bee-bread " from it. 



An example of a very close relation between floral construction and 

 the body of the visiting insect is afforded by the pollination of Salvia 

 pratenais by Humble Bees. Fig. 528, 1, shows a flower of Salvia with a 

 Humble Bee on the lower lip in search of nectar. The flower has 

 only two stamens, the two halves of each anther being quite differently 

 developed, and separated by an elongated connective ; the one half- 

 anther is sterile and forms a projection in the throat of the corolla- 

 tube, the other at the end of the long arm of the connective is fertile 

 and lies beneath the hood formed by the upper lip of the corolla. 

 The connective thus forms a lever, with unequal arms, movable on 

 the summit of the short filament. When the bee introduces its 

 proboscis it presses on the short arm of the lever; the fertile half- 

 anther is thus by the movement of the connective (c) on its place of 

 attachment to the filament (/) brought down against the hairy dorsal 



