FERTILIZATION OF FLOWERS. 359 - 



consists as usual of two anther-lobes united together by a con- 

 nective ; but the connective is very greatly elongated, so that the 

 anther- lobes are widely separated from one another instead of 

 lying close together at the top of the filament. The anther-lobe 

 at one end of each connective is imperfect and produces little or 

 no pollen ; the other is fully developed. The connective is 

 attached to the top of the very short filament by a movable joint, 

 so that it can be swung freely up and down in a vertical plane. 

 It has a long limb which curves upwards inside the " helmet " of 

 the corolla and terminates in the perfect anther-lobe, and a 

 short one which bears the imperfect lobe, as shown in the figure. 

 The two stamens lie side by side in the flower and the imperfect 

 anther-lobes are held downwards in the mouth of the corolla- 

 tube, exactly in the path of a visiting insect. The perfect anther- 

 lobes, on the other hand, are, at first, held up well above the 

 level of the insect's back (Fig. 181, st'). 



When a large insect, such as a bee, visits the flower, it alights 

 upon the large lower lip ( [/), which, as in so many other flowers, 

 affords a convenient platform and has doubtless been specially 

 adapted to that end. The head of the insect is then thrust into the 

 corolla-tube and pushes against the two imperfect anther-lobes. 

 The connectives turn on their pivots like a see-saw and the two 

 ripe anther-lobes (st") are clapped down on the back of the insect 

 and dust it with pollen. This happens when the insect visits a 

 young flower. When an older flower, in the female condition, is 

 visited, the pollen from the back of the insect is deposited on the 

 mature stigma (gr"), which now hangs directly in front of the 

 entrance to the corolla-tube. 



It is, however, in the highly specialized order Orchidaceae that 

 we find perhaps the most remarkable contrivances for ensuring 

 cross-fertilization that are to be met with in the vegetable 

 kingdom. Many of these have been described and illustrated by 

 Darwin in his well-known work on the " Fertilization of Orchids." 



In the common early orchis of Europe (Orcliis mascula, 

 Fig. 182) there are three sepals and three petals, and both sepals 

 and petals are brightly coloured. The lower petal is very large and 

 in front forms a tongue-like projection termed the labellum (u\ 

 which serves as a landing platform, while behind it is produced 

 backwards into a hollow spur or nectary (sp, ri) in which honey 

 is secreted. The reproductive organs lie just above and partly 

 in front of the entrance to the nectary, so that an insect, in 



