64 OPHRE.E. Chap IL 



beneath the two pouches. Now let us suppose an insect 

 to alight on one side of the labellum so as first to lick 

 up the exposed drop of nectar on this side ; from the 

 position of the pouch exactly over the drop, it would 

 almost certainly get the pollinium of this side attached 

 to its head. If it were now to go to the mouth of the 

 true nectary, the pollinium attached to its head from 

 not having as yet become depressed would not toucli 

 the stigma ; so that there would be no self-fertilisation. 

 The insect would then probably suck the exposed drop 

 of nectar on the other side of the labellum, and would 

 perhaps get another pollinium attached to its head ; it 

 would thus be considerably delayed by having to visit 

 the three nectaries. It would then visit other flowers 

 on the same plant, and afterwards flowers on a distinct 

 plant ; and by this time, but not before, the poUiuia 

 will have undergone the movement of depression and 

 will be in a proper position for efi'ecting cross-fertilisa- 

 tion. It thus appears that the secretion of nectar at 

 three separate points of the labellum, — the wide dis- 

 tance apart of the two rostella, — ^and the slow down- 

 ward movement of the caudicle without any lateral 

 movement — are all correlated for the same purpose of 

 cross-fertilisation. 



To what extent this Orchis is frequented by insects, 

 and what the kinds are, I do not know, but several of 

 the flowers on two spikes, sent me by the Rev. B. S. 

 Mahlen, had a single pollinium removed, and one 

 ilower had both removed. 



We now come to two genera, namely, Gymuadenia 

 and Habenaria or Platanthera, including four British 

 species, which have uncovered viscid discs. The viscid 

 matter, as before remarked, is of a somewhat difteren* 

 nature from that in Orchis, Ophrys, &c., and does not 



