of course, the last inch and a half filled with nectar.  Studying this appendage by the light of the principles he had laid down, Darwin ventured on a prophecy which roused special mirth among the unbelievers.  Not only the abnormal length of the nectary had to be considered; there was, besides, the fact that all its honey lay at the base, a foot or more from the orifice.  Accepting it as a postulate that every detail of the apparatus must be equally essential for the purpose it had to serve, he made a series of experiments which demonstrated that some insect of Madagascar—­doubtless a moth—­must be equipped with a proboscis long enough to reach the nectar, and at the same time thick enough at the base to withdraw the pollinia—­thus fertilizing the bloom.  For, if the nectar had lain so close to the orifice that moths with a proboscis of reasonable length and thickness could get at it, they would drain the cup without touching the pollinia.  Darwin never proved his special genius more admirably than in this case.  He created an insect beyond belief, as one may say, by the force of logic; and such absolute confidence had he in his own syllogism that he declared, “If such great moths were to become extinct in Madagascar, assuredly this Angraecum would become extinct.”  I am not aware that Darwin’s fine argument has yet been clinched by the discovery of that insect.  But cavil has ceased.  Long before his death a sphinx moth arrived from South Brazil which shows a proboscis between ten and eleven inches long—­very nearly equal, therefore, to the task of probing the nectary of Angraecum sesquipidale.  And we know enough of orchids at this time to be absolutely certain that the Madagascar species must exist.

FOOTNOTES: 

[Footnote 4:  Vide “The Lost Orchid,” infra, p. 173.]

[Footnote 5:  I have learned by a doleful experience that this fly, commonly called “the weavil,” is quite at home on Loelia purpurata; in fact, it will prey on any Cattleya.]

HOT ORCHIDS.

In former chapters I have done my best to show that orchid culture is no mystery.  The laws which govern it are strict and simple, easy to define in books, easily understood, and subject to few exceptions.  It is not with Odontoglossums and Dendrobes as with roses—­an intelligent man or woman needs no long apprenticeship to master their treatment.  Stove orchids are not so readily dealt with; but then, persons who own a stove usually keep a gardener.  Coming from the hot lowlands of either hemisphere, they show much greater variety than those of the temperate and sub-tropic zones; there are more genera, though not so many species, and more exceptions to every rule.  These, therefore, are not to be recommended to all householders.  Not everyone indeed is anxious to grow plants which need a minimum night heat of 60 deg. in winter, 70 deg. in summer, and cannot dispense with fire the whole year round.