As to the botanical limits of the genus, I must needs confess that they are exceedingly difficult to fix. It is as true now as when Professor Lindley first made the observation to me, that "The more we build up the partition walls between _Odontoglossum_, _Oncidium_, &c., the more the species break them down." Certainly no one at first sight would suppose _Odontoglossum cariniferum_ was anything but an _Oncidium_, nor _Oncidium macranthum_ other than an _Odontoglossum_. Indeed, I must own to a suspicion that ultimately both these genera, together with _Miltonia_, _Mesospinidium_, _Aspasia_, and possibly one or two others, may come to be regarded merely as _sub_-genera, But this difficult question is safest left in Professor Reichenbach's far abler hands. At the same time, it is not to be denied that there is such a peculiar look about the _Odontoglossa_, that even a non-scientific observer has seldom any difficulty in at once referring most of the species to their true position. One other matter remains to which I must very briefly advert. Mr. Darwin's fascinating work on the "Fertilization" of Orchids has led many persons to suppose that this beautiful tribe lends an exceptional amount of support to the theory with which that ingenious writer's name is so prominently associated, but there could scarcely be a greater mistake. Not only is the theory in question utterly rejected by Professor Reichenbach, the _facile princeps_ of living orchidists, but the greater our knowledge of the order, the less countenance does it seem to yield to the Darwinian view. We have now become perfectly well acquainted with all the genera--we might almost say with all the species--that belong to particular countries, but it is in these that the limits of variation between the different forms are most distinctly defined; in these, too, the great principle of unity in diversity is most conspicuous--the genera holding aloof from each other, and even the species keeping themselves distinct, although the Orchid mark is unmistakeably stamped upon all alike. Mr. Gould has remarked, in his great work on the "_Trochilidæ_," that the Darwinian theory derives no support from _them_, and the same may be safely affirmed of Orchids, which--we are now speaking of America--are the humming-birds' constant associates. Neither, while we contemplate the marvellous and inexhaustible variety of form by which the order is distinguished above all its fellows, can any plead that this result is due to its ancient lineage, nor yet to the vast periods through which endless transformations are assumed to have been continually taking place, because Orchids--according to geologic reckoning--are but a thing of yesterday, and have never been found in a fossil state. Yet their constant companions the Ferns, trace back their pedigree to the earliest vegetation of the primeval world! To the believer, however, the problem is not hard to solve. Ferns and other flowerless