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 Phalœnopsis Wightii, delicate of growth and small of flower, will become strong and generous by union with Phal. grandiflora, without losing its dainty tones.
It is worth mention that the first Flora medal offered by the Royal Horticultural Society for a seedling—a hybrid—in open competition was won by Lœlia Arnoldiana in 1891; the same variety took the first prize in 1892. It was raised by Messrs. Sander from L. purpurata × Catt. labiata; seed sown 1881, flowered 1891.
And now for the actual process by which these most desirable results, and ten thousand others, may be obtained. I shall not speak upon my own authority, which the universe has no reason to trust. Let us observe the methods practised in the great establishment of Mr. Sander at St. Albans.
Remark, in the first place, the low, unshaded range of houses devoted to hybridization, a contrast to those lofty structures, a hundred yards long or more, where plants merely flourish and bloom. Their span roofs one may touch with the hand, and their glass is always newly cleaned. The first and last demand of the hybridizer is light—light—eternally light. Want of it stands at the bottom of all his disappointments, perhaps. The very great majority of orchids, such as I refer to, have their home in the tropics; even the "cool" Odontoglots and Masdevallias owe that quality to their mountaineering habit, not to latitude. They live so near the equator that sunshine descends almost perpendicularly—and the sun shines for more than half the year. But in this happy isle of ours, upon the very brightest day of midsummer, its rays fall at an angle of 28°, declining constantly until, at midwinter, they struggle through the fogs at an inclination of 75°. The reader may work out this proportion for himself, but he must add to his reckoning the thickness of our atmosphere at its best, and the awful number of cloudy days. We cannot spare one particle of light. The ripening seed must stand close beneath the glass, and however fierce the sunshine no blind may be interposed. It is likely that the mother-plant will be burnt up—quite certain that it will be much injured.
This house is devoted to the hybridizing of Cypripediums; I choose that genus for our demonstration, because, as has been said, it is so very easy and so certain that an intelligent girl mastered all its eccentricities of structure after a single lesson, which made her equally proficient in those of Dendrobes, Oncidiums, Odontoglots, Epidendrums, and I know not how many more. The leaves are green and smooth as yet, with many a fantastic bloom, and many an ovary that has just begun to swell, rising amidst the verdure. Each flower spike which has been crossed carries its neat label, registering the father's name and the date of union.
Mr. Maynard takes the two first virgin blooms to hand: Cypripedium Sanderianum, and Cypripedium Godefroyæ, as it chances. Let us cut off the lip in order to see more clearly. Looking down now upon the flower, we mark two wings, the petals, which stood on either side of the vanished lip. From the junction of these wings issues a round stalk, about one quarter of an inch long, and slightly hairy, called the "column." It widens out at the tip, forming a pretty table, rather more than one-third of an inch long and wide. This table serves no purpose in our inquiry; it obstructs the view, and we will remove it; but the reader understands, of course, that these amputations cannot be performed when business is intended. Now—the table snipped off—we see those practical parts of the flower that interest us. Beneath its protection, the column divides into three knobbly excrescences, the central plain, those on either side of it curling back and down, each bearing at its extremity a pad, the size of a small pin's head, outlined distinctly with a brown colour. It is quite impossible to mistake these things; equally impossible, I hope, to misunderstand my description. The pads are the male, the active organs.
But the column does not finish here. It trends downward, behind and below the pads, and widens out, with an exquisitely graceful curve, into a disc one-quarter of an inch broad. This is the female, the receptive part; but here we see the peculiarity of orchid structure. For the upper surface of the disc is not susceptible; it is the under surface which must be impregnated, though the imagination cannot conceive a mere accident which would throw those fertilizing pads upon their destined receptacle. They are loosely attached and adhesive, when separated, to a degree actually astonishing, as is the disc itself; but if it were possible to displace them by shaking, they could never fall where they ought. Some outside impulse is needed to bring the parts together. In their native home insects perform that service—sometimes. Here we may take the first implement at hand, a knife, a bit of stick, a pencil. We remove the pads, which yield at a touch, and cling to the object. We lay them one by one on the receptive disc, where they seem to melt into the surface—and the trick is done. Write out your label—"Cyp. Sanderianum × Cyp. Godefroyæ, Maynard." Add the date, and leave Nature to her work.
She does not linger. One may almost say that the disc begins to swell instantly. That part which we term the column is the termination of the seed-purse, the ovary, which occupies an inch, or two, or three, of the stalk, behind the flower. In a very few days its thickening becomes perceptible. The unimpregnated bloom falls off at its appointed date, as everybody knows; but if fertilized it remains entire, saving the labellum, until the seed is ripe, perhaps half a year afterwards—but withered, of course. Very singular and quite inexplicable are the developments that arise in different genera, or even species, after fertilization. In the Warscewiczellas, for example, not the seed-purse only, but the whole column swells. Phalœnopsis Luddemanniana is specially remarkable. Its exquisite bars and mottlings of rose, brown, and purple begin to take a greenish hue forthwith. A few days later, the lip jerks itself off with a sudden movement, as observers declare. Then the sepals and petals remaining take flesh, thicken and thicken, while the hues fade and the green encroaches, until, presently, they assume the likeness of a flower, abnormal in shape but perfect, of dense green wax.
This Cypripedium of ours will ripen its seed in about twelve months, more or less. Then the capsule, two inches long and two-thirds of an inch diameter, will burst. Mr. Maynard will cut it off, open it wide, and scatter the thousands of seeds therein, perhaps 150,000, over pots in which orchids are growing. After experiments innumerable, this has been found the best course. The particles, no bigger than a grain of dust, begin to swell at once, reach the size of a mustard-seed, and in five or six weeks—or as many months—they put out a tiny leaf, then a tiny root, presently another leaf, and in four or five years we may look for the hybridized flower. Long before, naturally, they have been established in their own pots.