Hybridising
Most of the so-called Florists' Flowers have been brought up to their present standard of excellence by careful and systematic Hybridisation. The mere operation is easy enough; it is simply necessary to convey the pollen, by means of a camel-hair brush, or otherwise, from the male parent, and place it on the stigmatic surface of the flower of the female, or seed-bearer. Of course, unless the latter is receptive, this proceeding would be ineffective. As a rule, when it is fit to be acted upon by the pollen, the stigma becomes more or less glutinous; in some plants, this condition occurs before their own anthers are ready to discharge the pollen, and in others after the pollen has been shed. In both these cases, the arrangement is evidently to prevent self-fertilisation. Not a few plants, however, develop stigma and anthers at the same time, and with them it is necessary to remove the anthers before they burst, and, at the same time, by means of fine gauze or otherwise, to prevent the visits of insects, which might convey pollen from another flower, and thus effect an undesirable cross. Continuously working with pollen of certain flowers not unfrequently conduces to sterility, and then a fresh strain must be used, possessing one or more of the qualities it is wished to perpetuate and improve. For instance, a flower of good form, but defective in colour, is, perhaps, crossed with another which is faulty in shape, but of a novel and desirable shade. A weakly-growing variety, of good habit, may be used with effect in combination with a stronger grower lacking the particular qualities present in the former. Sometimes, the florist's ideal has been kept so constantly in sight, that the pollen of a particular strain becomes more or less abortive. More than one very successful raiser of Cyclamens and Gladioli habitually call in the aid of the microscope to determine the state of the pollen in highly-bred seedlings. If this is uneven--not plump, clean and regular--in size and outline, the plant is discarded as a male parent, and another chosen (with perfect pollen) which promises to attain the desired results in size, form, or colour of flower. Hybrids between two distinct genera are by no means common. A good example is Philageria (a cross between the beautiful climbing Lapageria rosea and the bushy Philesia buxifolia), which is intermediate in character between its two parents, though not nearly so desirable as either. Species of the same genus frequently refuse altogether to cross with each other, and some, again, will only cross one way. No definite rules can be laid down, and exceptions can only be learned by experience.
The following remarks, anent double flowers, are taken from a lecture by the Hon. Marshall P. Wilder, delivered before the Massachusetts Horticultural Society, some thirteen years ago. The gentleman in question is a well-known and very successful hybridiser. "In my experiments, I have discovered that, for the production of double flowers, it is important that the pollen used for impregnation should be borne on a petaloid anther--that is, an anther bearing a small petal--and that this is still better if from a double flower. I also observed, that the larger and better developed this petaloid anther, the better chance for a fine double offspring; for, as might have been expected, the anthers being connected with the corolla, the number of petals would be increased by such an operation. I found, also, that, for the most perfect and symmetrical flowers, it was better to select single flowers, which were the most perfect in their petals, for seed-bearers; and that single or semi-double sorts with perfect corollas, when impregnated with petaloid pollen, will produce double flowers of a regular symmetrical formation. Of this I have the most conclusive evidence in the Camellia Wilderi, and many other fine double varieties in my collection, which were produced from the single red and single white Camellias, fertilised by pollen from a petaloid anther of double varieties."