Having thus had one initiation into this most enticing realm of riddles, each successive orchid whose structure we examine from this stand-point becomes a most interesting, perhaps a fresh, problem, whose assumed solution may often be verified by studying the insect in its haunts. Darwin thus foretold the precise manner of the cross-fertilization of _Habenaria mascula_, and also the insect agent, simply by the structural prophecy of the flower itself. Suppose, for example, an unknown orchid blossom to be placed in our hands. Its nectary tube is five inches in length, and as slender as a knitting-needle. The nectar is secreted far within its lip. The evolution of the long nectary implies an adaptation to an insect's tongue of equal length. What insect has a tongue five inches long, and sufficiently slender to probe this nectary? The sphinx-moth only. Hence we infer the sphinx-moth to be the insect complement to the blossom, and we may correctly infer, moreover, that the flower is thus a night-bloomer. Examination of the flower, with the form of this moth in mind, will show other adaptations to the insect's form in the position of pollen and stigma, looking to the flower's cross-fertilization. In some cases this is effected by the aid of the insect's tongue; in others, by its eyes. In our own native orchids we have a remarkable example of the latter form in the _Habenaria orbiculata_, whose structure and mechanism have also been admirably described by Asa Gray. [Illustration: Fig. 5] All orchid-hunters know this most exceptional example of our local flora, and the thrill of delight experienced when one first encounters it in the mountain wilderness, its typical haunt, is an event to date from--its two great, glistening, fluted leaves, sometimes as large as a dinner-plate, spreading flat upon the mould, and surmounted by the slender leafless stalk, with its terminal loose raceme of greenish-white bloom. [Illustration]