150 THE STRUCTUEE OF FLOWERS, 



One more point may he noticed in connection with tlie 

 above-mentioned correlations, namely, the motility of many 

 stamens. This is always in reference to fertilisation, and, 

 if it be an adaptation to intercrossing, then the anther takes 

 up such a position that the insect strikes it when searching 

 for honey, as in the Aconite and Tropceolum. If, on the 

 contrary, the motion is to secure self-fertilisation, then it 

 is regardless of the honey, and may actually interfere 

 with the access to it by insects, as in the Bosacece : for in 

 members of this order, with an indefinite number of stamens, 

 the further they spread away from the pistil the more readily 

 is the honey accessible ; but when they curve inwards, and 

 crowd over the stigmas in the centre, they completely cover 

 up and conceal the honey-disk. 



The position of the anthers in relation to the honey- 

 secreting organs will, I think, often be found to be the clue 

 to certain anomalies in flowers. Thus in Geranium pratense 

 it has been noticed that the petaline stamens stand ulti- 

 mately externally to the calycine. Now, the position of the 

 five glands in front of the sepals requires that a tubular space 

 should exist above them, down which an insect may thrust 

 its proboscis, as in the Wallflower. Consequently the five 

 stamens in front of the sepals must be so disposed as not to 

 interfere wnth this passage. This can only be secured by 

 their bending well inwards towards the styles below, and 

 then outwards, above, so as to bring the anthers again on 

 the same vertical plane as those of the petaline stamens. 



The more internal position of the calycine stamens, and 

 the external position of the petaline ones, are immediately due 

 to the gland, so to say, forcing the former inwards, while 

 the buttress-like bases of the carpels thrust the latter out- 

 wards. This gives rise to the so-called obdiplostemony of 

 the GeraniacecG. 



