238 THE FLOWER. 



false coadaptation." The whole arrangement is displaj'ed in 

 the annexed diagram (Fig. 470) , and in the following account 

 of the operation. 1 " In a state of nature, the flowers are inces- 

 santly visited for their nectar by hive and other bees, various 

 'Diptera, and Lepidoptera. The nectar is secreted all round the 

 base of the ovarium ; but a passage is formed along the upper 

 and inner side of the flower by the lateral deflection (not repre- 

 sented in the diagram) of the basal portions of the filaments ; 

 so that insects invariably alight on the projecting stamens and 

 pistil and insert their proboscides along the upper and inner 

 margin of the corolla. We can now see why the ends of the 

 stamens with their anthers and the end of the pistil with the 

 stigma are a little upturned, so that they may be brushed by 

 the lower hairy surfaces of the insects' bodies. The shortest 

 stamens, which lie enclosed within the calyx of the long- and 

 mid-styled forms can be touched only by the proboscis and narrow 

 chin of a bee : hence they have their ends more upturned, and 

 they are graduated in length, so as to fall into a narrow file, 

 sure to be raked by the thin intruding proboscis. The anthers 

 of the longer stamens stand laterally farther apart and are more 

 nearly on the same level, for they have to brush against the 

 whole breadth of the insect's body. . . Now I have found no 

 exception to the rule that, when the stamens and pistil are bent, 

 they bend to that side of the flower which secretes nectar. . . . 

 When nectar is secreted on all sides, they bend to that side 

 where the structure of the flower allows the easiest access to it, 

 as in Lythrum. ... In each of the three forms, two sets of sta- 

 mens correspond in length with the pistil in the other two forms. 

 When bees suck the flowers, the anthers of the longest stamens, 

 bearing the green pollen, are rubbed against the abdomen and 

 the inner sides of the hind legs, as is likewise the stigma of the 

 long-styled form. The anthers of the mid-length stamens and 

 the stigma of the mid-styled form are rubbed against the under 

 side of the thorax and between the front pair of legs. And, 

 lastly, the anthers of the shortest stamens and the stigma of the 

 short-styled form are rubbed against the proboscis and chin ; for 

 the bees in sucking the flowers insert only the front part of their 

 heads into the flower. On catching bees, I observed much green 

 pollen on the inner sides of the hind legs and on the abdomen, 

 and much yellow pollen on the under side of the thorax. There 

 was also pollen on the chin, and, it may be presumed, on the 

 proboscis, but this was difficult to observe. I had, however, 



* All from Darwin, Forms of Flowers, 137-147, &c. 



