The common motive for crossing orchids is that, of course, which urges the florist in other realms of botany. He seeks to combine tints, forms, varied peculiarities, in a new shape. Orchids lend themselves to experiment with singular freedom, within certain limits, and their array of colours seems to invite our interference. Taking species and genera all round, yellow dominates, owing to its prevalence in the great family of Oncidium; purples and mauves stand next by reason of their supremacy among the Cattleyas. Green follows--if we admit the whole group of Epidendrums--the great majority of which are not beautiful, however. Of magenta, the rarest of natural hues, we have not a few instances. Crimson, in a thousand shades, is frequent; pure white a little rare, orange much rarer; scarlet very uncommon, and blue almost unknown, though supremely lovely in the few instances that occur. Thus the temptation to hybridize with the object of exchanging colours is peculiarly strong.
It becomes yet stronger by reason of the delightful uncertainty which attends one's efforts. So far as I have heard or read, no one has yet been able to offer a suggestion of any law which decides the result of combination. In a general way, both parents will be represented in the offspring, but how, to what degree either will dominate, in what parts, colours, or fashions a hybrid will show its mixed lineage, the experienced refuse to conjecture, saving certain easy classes. After choosing parents thoughtfully, with a clear perception of the aim in view, one must "go it blind." Very often the precise effect desired appears in due time; very often something unlooked for turns up; but nearly always the result is beautiful, whether or no it serve the operator's purpose. Besides effect, however, there is an utility in hybridization which relates to culture. Thus, for example, the lovely _Cypripedium Fairieanum_ is so difficult to grow that few dealers keep it in their stock; by crossing it with _Cyp. barbatum_, from Mount Ophir, a rough-and-ready cool species, we get _Cyp. vexillarium_, which takes after the latter in constitution while retaining much of the beauty of the former. Or again, _Cypripedium Sanderianum_, from the Malay Archipelago, needs such swampy heat as few even of its fellows appreciate; it has been crossed with _Cyp. insigne_, which will flourish anywhere, and though the seedlings have not yet bloomed, there is no reasonable doubt that they will prove as useful and beautiful as in the other case. _Cypripedium insigne_, of the fine varieties, has been employed in a multitude of such instances. There is the striking _Cyp. hirsutissimum_, with sepals of a nameless green, shaded yellow, studded with spiculæ, exquisitely frilled, and tipped, by a contrast almost startling, with pale purple. It is very "hot" in the first place, and, in the second, its appearance would be still more effective if some white could be introduced; present it to _Cyp. niveum_ and confidently expect that the progeny will bear cooler treatment, whilst their "dorsal sepal" will be blanched. So the charming _Masdevallia Tovarensis_, warm, white and lowly, will take to itself the qualities, in combination, of _Mas. bella_, tall, cool, and highly coloured red and yellow, as Mr. Cookson has proved; so _Phaloenopsis Wightii_, delicate of growth and small of flower, will become strong and generous by union with _Phal. grandiflora_, without losing its dainty tones.