Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/94

74 attached, and there is hardly a vestige of the rudimentary tail. In fig. 12 the discs of both species, of the proper proportional sizes, are represented as seen vertically from above. The pollinia, after removal from their cells, undergo nearly the same movements as in the last species. In both forms the movement is well shown, by removing a pollinium by the thick end with a pair of pincers, and holding it under the microscope, when the plane of the viscid disc will be seen to move through an angle of at least forty-five degrees. The caudicles of the Lesser Butterfly Orchis are relatively very much shorter than in the other species; the little packets of pollen are shorter, whiter, and, in a mature flower, separate much more readily from one another. Lastly, the stigmatic surface is differently shaped, being more plainly tripartite, with two lateral prominences, situated beneath the viscid discs. These prominences contract the mouth of the nectary, making it subquadrangular. Hence I cannot doubt that the Larger and Lesser Butterfly Orchids are distinct species, masked by close external similarity.

As soon as I had examined the present species,