Chai'. IV. EPIPACTIS PALUSTPvIS. 97 



landing-place for insects, is joined to the basal half by 

 a narrow hinge, and naturally (fig. A) is turned a little 

 upwards, so that its edges pass within the edges of the 

 basal portion. So flexible and elastic is the hinge that 

 the weight of even a fly, as Mr. More informs me, 

 depresses the distal portion ; it is represented in fig. B 

 in this state ; but when the weight is removed it 

 instantly springs up to its former position (fig. A), and 

 with its curious medial ridges partly closes the entrance 

 into the flower. The basal portion of the labellum forms 

 a cup, which at the proper time is filled with nectar. 



Now let us see how all the parts, which I have been 

 obliged to describe in detail, act. When I first ex- 

 amined these flowers I was much perplexed : trying in 

 the same manner as I should have done with a true 

 Orchis, I slightly pushed the protuberant rostellum 

 downwards, and it was easily ruptured ; some of the 

 viscid matter was withdrawn, but the pollinia remained 

 in their cells. Reflecting on the structure of the 

 flower, it occurred to me that an insect in entering one 

 in order to suck the nectar, would depress the distal 

 portion of the labellum, and consequently would not 

 touch the rostellum ; but that, when within the flower, 

 it would be almost compelled, from the springing up 

 of this distal half of the labellum, to rise a little up- 

 wards and back out parallel to the stigma. I then 

 brushed the rostellum lightly upwards and backwards 

 with the end of a feather and other such objects ; and 

 it was pretty to see how easily the membranous cap 

 of the rostellum came off, and how well from its elas- 

 ticity it fitted any object, whatever its shape might be, 

 and how firmly it clung to the object owing to the 

 viscidity of its under surface. Large masses of pollen, 

 adhering by the elastic threads to the cap of the ros- 

 tellum were at the same time withdrawn. 



