THE ORIGIN OF FLOWERS 



187 



are quite closed by day. This is the case with the large, white, scent- 

 less bindweed (Convolvidus sepium), which is chiefly visited and 

 fertilized by the largest of our hawk-moths (Sphinx convolvuli). The 

 pale soapwort {Sapoiiaria officinalis) exhales a delicate fragrance 

 which attracts the Sphingidse from afar, and the sweet smell of the 

 honeysuckle {Lonicera periclymenum) is well known, and has the same 

 effect ; an arbour of honeysuckle often attracts whole companies of our 

 most beautiful Sphingidte and Noctuidae on warm June nights, to the 

 great delight of the moth-collecting youtli. 



Fig. 45. Baphtie mesereum {A and C) and Daphne striata (B and D). The 

 former visited by butterflies, bees, and flies, the latter by butterflies only. 

 A and S, vertical sections of tlie flowers. St, stamens. Gr, style, n, nectary. 

 C and D flov^ers seen from above. After H. Miiller. 



I cannot conclude this account of flower-adaptations without con- 

 sidering the orchids somewhat more in detail, for it is among them 

 that we find the most far-reaching adaptations to the visits of insects. 

 Among them, too, great diversity prevails, as is evident from the fact 

 that Darwin devoted a whole book to the arrangements for fertilization 

 in orchids, but the main features are very much the same in the 

 majority. Figure 46 gives a representation of one of our commonest 

 species [OrcJds mascula), A shows the flower in side view, 5 as it 

 appears from in front. The flower seems as it were to float on the 

 end of the stalk (st), stretching out horizontally the spur (sp) which 

 contains the nectar. Between the large, broad under lip ( U), marked 

 with a honey-guide (sm), and offering a convenient alighting surface, 

 and the broad, cushion-like stigma (n) lies the entrance to the spur. 

 Fertilization occurs in the following way : — The fly or bee, when it is 

 in the act of pushing its proboscis into the nectar-containing spur. 



