This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
II. We know there are a few genera, such as Rhododendrons, Pansies, Fuchsias, Roses, Verbenas, etc, in which the species do readily hybridize. These genera are very few ; but our critics insist that the vine is one of them. Grant it for the moment, will not "the constitutional debility, if not the invariable sterility of the hybrid offspring" be likely to render it useless in the vineyard? If a plant, in the greenhouse or flower garden, have even but a moderate constitutional vigor, sterility renders it all the more desirable. In a fertile plant, says De Candolle, the withering and fall of the coral of a flower is determined by a perfect fertilization, and takes place more or less promptly as the fecundation is more or less complete. Then all the accumulated nourishment and juices of the plant go to perfect the seed. If no fecundation, or an imperfect one takes place, a part of the juices of the plant continue to nourish and sustain in beauty and freshness the corollas already expanded, while the remaining elaborated nourishment is diverted to the formation of new flowers.
It is from not seeding freely that, in the case of double flowers, each individual flower continues longer expanded before withering, a fresh succession of blooms is thrown up, and still the plant is far less exhausted than if it had borne seed. Single dahlias continue in bloom but a short time, and each flower is transient, and the small tubers show how little nourishment is laid up for another season. The double dahlia on the contrary, blooms through the season, and in this case, as in general, the more double the flowers of a plant may be the longer will each flower remain fresh; the more continuedly will it be in flower; and if a perennial, the better state will it be in for blooming finely the ensuing year. Hybrid plants seldom or never producing perfect seed, their unfertilized flowers retain the nourishment nature destines for the germ, gorging the existing petals with accumulated juices; another portion of which often goes to develope new petals, rendering the flower more or less double; or if the plant still remains single, yet from the same cause, (its sterility,) presenting a like persistance, profusion, and renewal of its bloom. To produce and ripen its seed, is the greatest drain upon its vitality to which a plant is subjected.
Annuals and biennials, if not suffered to seed, can often be made of perennial duration. On the contrary, who has not seen vines and fruit trees which have exhausted themselves and perished in maturing too large a crop? But the hybrids of the flower garden being generally subjected to the most favorable conditions as to care and nourishment, especially as they are seldom taxed with maturing seed, can be kept in health and beauty even if there does exist some tendency to constitutional debility. Here, then, hybrids are deservedly great favorites, and the accomplishment of more than we expected from our efforts in hybridizing flowering plants has led us to expect more than we are likely to accomplish by our efforts in hybridizing fruit bearing ones. While our fruit books are filled with the names of chance seedlings of great excellence, the labors of the hybridizer thus far have given us only the promise of good things to come. Not a single hybrid fruit is yet in general cultivation.
Do we owe much more to cross-breeding? Of the nearly three thousand varieties described in the new edition of Downing's Fruits, are there thirty that with any show of reason are claimed to be cross-bred? Of these, are there over three first class fruits? All the results of Mr. Knight's trials in crossing the pear, with one exception, (Pengethby,) are placed by Downing in the third class among the rejected. Mr. Berckmans writes me, that "Dr. Brinckle has tried cross fertilizing. I have all his grafts, over five hundred with pedigree and lineage. His chance seedlings from good pears, supercede all his laboriously fertilized ones, most of which present a very dubious character, some being entirely wild, slender or sickly." No one will claim that the proportion of good fruits hitherto raised by crossing varieties has been greater than from the chance seedlings of the same varieties without cross impregnation. If Providence had left mankind from the creation until Knight was born to depend upon cross fertilization for good fruits, very possibly he might have been born into a world where no fruit trees were left to be crossed.
They would already have been exterminated as worthless.
To originate improved varieties of fruit, let us then no longer look to hybridization; for if the operation is successful, the resulting plant is very likely to be debilitated, if not sterile; neither to cross fertilizing varieties, for the manipulation requires the nicest care; and, as we have seen, is quite uncertain in its results. Even if as is claimed we could in hybridizing, thereby combine all the separate excellences of the two species crossed, (" and the offspring of a hybrid has never been known to possess a character foreign to its parents,") we could at best obtain in the result only the sum of the excellences of the two parents. So in crossing varieties. By what blending all the excellences of the two best pears existing seventy-five years since, could we have reached the matchless flavor of Belle Lucrative or Seckel? Could any crossing among our harsh and worthless native grapes by combining existing flavors, have produced such grapes as Lenoir and Warren? And yet without the slightest proof of such intermixture, and still less of a foreign cross, what a number of really valuable native varieties have sprung up the last few years. These fruits are not merely the sum of existing excellences.
III. How, then, shall new varieties be obtained? Obviously by following the practice of those who already really have succeeded. Let us take advantage of the tendency to sport, more or less inherent in all fruit-bearing plants, that have already left in some degree the wild state, or which, while still wild and harsh, are by cultivation subjected to new influences and conditions. It is not enough, however, merely to sow the seeds of good fruits, as " Poiteau tells us, that Duhamel during the long course of his scientific career planted the seeds of all the best fruits which were eaten at his table, without being able to produce a single fruit worthy of cultivation. The Alfroys had during three successive generations adopted the same course, and with no better success," (Kenrick.) Van Mon's first seedlings, also from the old decayed varieties, such as Choumontel, St Germain, etc., Mr. Berckmans informs me, gave him no good result, but returned at once to their wild state. He presently found, other things being equal, "the older a pear is of any cultivated variety, the nearer will the seedlings raised from it approach the wild state." " He was more successful in the progeny of these wildings, but still more so when he resorted to the seeds of the then recently improved varieties originated by Duquesne, and Hardenpost, Ac. From the seeds of such renovated varieties as Glout Morceau, Napoleon, Marie Louise, and especially Passe Colmar, his best pears were derived.