Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/60

40 between the two membranes. So copious is this fluid, that, after cutting off the extremities of the nectaries of O. pyramidalis, and gently squeezing them on glass under the microscope, such large drops of fluid exuded from the cut ends, that I concluded that at last I had found nectaries which contained nectar; but when I carefully made, without any pressure, a slit along the upper surface of other nectaries from the same plants, and looked into them, their inner surfaces were quite dry.

I then examined the nectaries of Gymnadenia conopsea (a plant ranked by some botanists as a true Orchis) and of Habenaria bifolia, which are always full of nectar up to one-third or two-thirds of their length. The inner membrane presented the same structure and was covered with papillæ as in the foregoing species; but there was a plain difference in the inner and outer membranes being closely united, instead of being in some degree separated from each other and charged with fluid. I was therefore led to conclude that insects penetrate the lax inner membrane of the nectaries of the above-named Orchids, and suck the copious fluid between the two membranes. This was a bold hypothesis; for at the time no case was known, of insects penetrating with their delicate proboscides even the laxest membrane. But I have now heard from Mr. Trimen, that at the Cape of Good Hope moths and butterflies do much injury to peaches and plums by puncturing their unbroken skins. In Queensland, Australia, a moth, the Ophideres fullonica, bores through the thick rind of the orange with its wonderful proboscis, provided with formidable teeth. There is therefore not the least difficulty in believing that Lepidoptera with their delicate proboscides, and bees