GRAFTING EMBRYOS.

383

as they advanced in growth, ended by becoming half incorporated, notwithstanding they ended by finally becoming a twin fruit, consisting of two very unequal halves. In the smaller fruit four cells for seeds were formed, but in the larger but three. In other respects the structure was complete, but each was furnished with a vein of elevated lines on the side next the junction. The nature of these is unknown to us. What is particularly deserving of attention here is, that the hairy surface of the young apple offered no obstacle to the junction in question; possibly it took place before the hairs were formed. It remains to be proved by practice, but certainly appears a possible, but exceedingly difficult operation."

CHAPTER XII.

THE PRODUCTION OF NEW VARIETIES.

CHANGE IN THE VEGETABLE WORLD EFFECT OF CLIMATE, SOIL, AND POSITION CULTIVATION, DEGENERACY, OR DETERIORATION - DECREPITUDE — Methods of PRODUCTION-SELECTION — VAN MONS' THEORY AS DISTINGUISHED FROM IT-CULTIVATED FRUITS NOT DESCENDED FROM THEIR MILD TYPES IMPORTANCE OF SECURING SEED FROM A YOUNG TREE- HYBRIDIZATION -EXPERIMENTS OF KOLREUTER, HERBERT, KNIGHT, GAERTNER, LINDLEY, PURKINJE, MIRBEL, ADOLPHE BROGNIART, CONRAD SPRENGEL, CASSINI, ALPHONSE DE CANDOLLE, SCHLEIDEN, FRITSCHE, THWAITES, MR. ROGERS—MANNER OF OPERA

TION.

NE of the most interesting properties of vegetable, as well as animal nature, is its susceptibility to change. This does not extend, however, to species, genera, orders, or classes, but is confined to varieties; thus the seed of a pear or apple will always produce the same species of fruit, while a variety of these species always originates in its offspring a totally different character; and the improvements of which these varieties are capable, through the skill of man, are without end. Let us consider some of the means which man makes use of to create these changes.

Difference of climate. It is evident that, if a variety of peach or other fruit be brought from a

INFLUENCE OF CLIMATE UPON OFFSPRING.

385

warm climate to a cooler one, the effect would be to stunt its vigor, prevent the perfect ripening of the fruit, as well as that of the wood. A seedling raised from such a tree, we should expect, would be possessed of less vigor than its parent, bear fruit of inferior quality than when in its native clime, at the same time that it would gain greater hardiness of wood, which would adapt it to its new position. If this same tree should be removed from its native clime to another, more favorable, it would find physical influences as unadapted to its character as the parent found in its place of nativity, and the next generation would return again to the first type. Thus through successive generations nature adapts the variety to the conditions in which it is placed. Mr. Knight, in a paper which he read before the London Horticultural Society, in 1806, said: "If two plants of the vine, or other tree of similar habits, or even if obtained from cuttings of the same tree, were placed to vegetate during several successive seasons in very different climates, the one planted on the banks of the Rhine, and the other on those of the Nile, each would adapt its habits to the climate in which it was placed; and if both were subsequently brought in early spring to a climate similar to that of Italy, the plant from the north would instantly vegetate, while the other would remain torpid." We think, however, that the observation of Mr. Knight has not been sus

386

CULTIVATION AFFECTING THE OFFSPRING.

tained by subsequent investigation, and that it has been found that the qualities of the plant itself do not vary so much as he then believed. If this had been so, the foreign varieties of peach in this country should have obtained something near the hardiness of our native varieties. It is true that conditions may exist which will bring out in bolder relief some inherent quality which they possessed, and which was not evident in the country from which they came, because the influence did not exist to mature them; and in their new position these qualities, thus strongly brought out, may be stamped strongly upon their offspring; yet we have no reason to believe that the constitution of the plant itself will be in the least degree altered.

Soil and position also influence the character of the offspring of fruit trees. Thus a pear tree requiring for its successful cultivation a light soil, if planted upon heavy land will be likely to produce progeny suited to such a soil. This, however, depends upon the care and skill used in its cultivation. If it be neglected, and the soil be cold and wet, it will be likely to entail disease upon the next generation, when proper cultivation would have secured an invaluable variety.

Cultivation. This does not improve the character of the plant itself, but has an immense influence to induce hardiness, vigor, early maturity, and productiveness. Those particular means should be used

DETERIORATION OF VARIETIES.

387

which will have the effect to bring out prominently some desirable trait in the offspring. If hardiness is desired, those methods should be employed which shall conduce to the perfect ripeness of the wood of the parent tree; if vigor, those which shall produce this; if early maturity and productiveness, vigorous summer pinching and root-pruning, to produce such in the parent.

It may be suggested by some that there is no necessity for the production of new sorts as long as we have those which are delicious, and which satisfy our wants. But it must be remembered that varieties have a limit of existence. They increase in strength until they reach an age like that of manhood in the human race, when deterioration and decay commences. This is not confined to the original seedling tree, but extends to all the buds or scions obtained from it directly or indirectly. Thus, if we do not produce new sorts, the standard of excellence will become very much lower by the deterioration of the older kinds, and at last none will be left worth cultivation. This can be seen in the fact that many of the sorts which were once vigorous, hardy, and easily grown, with ordinary cultivation, now resist the nicest conditions to their production and health. The St. Germain pear was once remarkably fine and beautiful in this country, and was cultivated with comparative ease; but now it is almost impossible to bring it to any degree of