114 THE STRUCTURE OF FLOWERS. 



responsive action on the other, coupled, of course, with here- 

 ditary and other influences which fix the variation. Thus, 

 then, aa I believe, all flowers as we have them now, which 

 are in perfect adaptation to insect agency, are the outcome 

 of the resultant of all the forces, external and internal, which 

 the insect has actually brought into play or stimulated into 

 action by visiting them for their honey or pollen. 



The belief that such processes may have gi-own in 

 response to mechanical irritations is supported by some 

 interesting experiments made by Mr. O'Brien, of Harrow, 

 who has kindly favoured me with the following remarks: 

 " With reference to impressions conveyed by ' nervous ' force 

 in Orchid flowers, whereby the expansion of the sepals and 

 petals signifies to the reproductive organs that the time for 

 fertilisation has arrived, I have observed that the periods of 

 maturing and of decay may be either arrested or hastened in 

 certain orchids by artificial means. With reference to arrest- 

 ing decay, I took such flowers as Stanhopea and Goryanthes, 

 which have large membranous sepals, and which, in the 

 ordinary course of events, become reflexed soon after the 

 opening of the flowers, and shortly afterwards wither. 

 These are then followed by the other parts. By seizing the 

 opportunity as soon as they expand, and by passing a thread 

 round them, so as to keep them in the condition of the flower 

 when just on the point of expansion, they may be kept good 

 for a long time, the flowers evidently, as it were, not 

 realizing the increased lapse of time, and being unaware that 

 they had passed the period when they would have been ready 

 for fertilisation. When so secured, a flower of Goryanthes 

 speciosa on my table kept fresh three times as long as it 

 would have done on the plant. The dripping of the water 

 from the horns above the bucket is also arrested. Finally, 

 on releasing the ligature, the broad wing-like sepals imme- 



