188 



THE EVOLUTION TIIEOIJY 



knocks with its head agjiinst the so-called rostclhim (?•), a little beak- 

 like process at the luise of the stamens (p). The pollen masses are of 

 very peculiar construction, not fallinoj to dust, but forming little 

 stalked clubs, with the pollen grains glued together, and so arranged 

 that they spring off when the rostellum is touched and attach them- 

 selves to the head of the insect, as at D on the pencil (Fig. 46). When 

 the bee has sucked up the nectar out of the spur, and then proceeds to 

 penetrate into another flower of the same species, the pollinia have 

 bent downwards on its forehead (E), and must unfailingly come in 

 contact with the stigma of the second flower, to which they now 



Fig. 46. Common Orchis {Orchis mascula). A, flower in side view, st, 

 stalk, sp, spur with the nectary (n). ei, entrance to the spur. U, lower lip. 

 B, flower from in front, p, pollinia. Sm, honey-guide, ei, entrance to the 

 nectar, wa, stigma, r, rostellum. U, lower lijj. C, vertical section through 

 the rostellum [r), pollinium (p). ei, entrance. D, the pollinia removed and 

 standing erect on the tiji of a lead-j^encil. E, the same, somewhat later, 

 curved downwards. 



remain attached, and effect its fertilization. What a long chain of 

 purposeful arrangements in a single flower, and no interpretation of 

 them is available except through natural selection ! 



And how diversely are these again modified in the different 

 genera and species of orchids, of which one is adapted to the visits of 

 butterflies exclusively, as Orchis ustulata, another to those of bees, as 

 Orchis morio, and a third to those of flies, as Ophrys miuscifera. These 

 flowers are adapted to insect visits in the minutest details of the form 

 of the petals, which are smooth, as if polished with wax, where insects 

 are not intended to creep, but velvety or hair}^ where the path leads 



