SEVERAL correspondents have requested our opinion concerning the respective merits of root-grafting and budding or stock-grafting, in the propagation of apple trees. A considerable degree of interest has recently been awakened on this subject, from the fact that at the late meeting of the North-Western Pomological Association, held at Dixon, 111., it was a prominent topic of discussion, and elicited a variety of opinions and experience among the nurserymen and orchardists of the west, to which we shall presently allude. Before proceeding further, it may be well to explain precisely what we mean by root-grafting. It is a very common practice among apple tree growers, and especially when stocks are scarce, to cut the roots of seedlings into sections or pieces two or three inches in length, and graft on these; thus making three or four trees of one root. But this is an abuse of root-grafting, and should not be recommended or practiced under any circumstances, although we admit that good trees are grown in this way, of some very free, vigorous growing varieties.

What we intend to speak of as root-grafting, is that in which the upper portion of a seedling root only is used, and the graft or scion inserted on the collar, or point of union between the root and stem of the plant.

In the Western States, the fresh and wonderfully fertile soil produces a rank and rapid growth of trees, and this continues unabated until a very late period of the autumn. Winter sets in upon these soft and succulent trees with the most sudden and violent changes of temperature - during the day a clear, bright sun, gives almost a summer warmth, while at night the mercury descends to zero, and even, in many cases, far below. This, it must be admitted, is a trying state of things. The upper parts of the trees seem to escape any very fatal injury, partly perhaps because they are gradually thawed by the gently rising heat of the morning, while at the 6urface of the ground the greatest injuries are sustained, owing perhaps to the sun striking that part from a greater altitude and from the heat reflected against it by the warmed surface of the ground. At that point, the bark is blackened and ruptured. Certain varieties are peculiarly liable to this, especially late growers. The Roxbury Russet and American Golden Russet are quoted as examples; but the Baldwin, Greening, and many others, are occasionally so affected, in proportion, probably, as the soil may be favorable, or otherwise, to the production of a late immature growth.

Now it is very evident that root-grafting is not a safe method of propagation for such varieties as are liable to these injuries in winter, but that they must be budded or grafted on stocks at such a distance from the ground as will place them beyond the reach of this influence. There can be no diversity of opinion on this point The question of practical interest is, which are tender varieties and which are not! and this must be answered by experience. We apprehend that the soil has very much to do with this matter. It is quite possible that some of the varieties complained of as being liable to winter-killing would entirely escape on a dry, elevated soil, where the growth would be moderate and the wood consequently well ripened. But people must take the soil as it is, and adapt their system of cultivation to its particular characteristics.

We suspect that in the West root-grafting is too often performed by using pieces instead of whole roots, and this accounts for trees - as spoken of in the Dixon Report - requiring the support of stakes for several years in the orchard. It is a fact, that trees propagated in this way do not produce a well proportioned development of roots. It is not uncommon to see such trees seven or eight feet high with only three or four prongs of roots, a few inches long, that one could hardly suppose capable of supporting such a growth of top; but trees propagated on whole roots are seldom if ever found in this condition.

As far as tardiness of bearing and unproductiveness are charged upon root-grafting, a pretty long and extensive experience compels us to regard it as an error; on the contrary, we have found that root-grafted trees, as a general thing, are, if anything, more fruitful than budded ones. It is quite common to see three or four year old root-grafted trees of certain sorts produce fruit in the nursery rows. Where in the world can more healthy and productive apple orchards be found than in Western New York, where ten years ago such a thing as budding or stock-grafting apple trees was scarcely thought of, and which to this day is practiced only on a very limited scale, for certain weak-growing sorts.

Mr. Hovey says: "We have long been convinced that it was a perfect waste of time and money to plant root-grafted trees, and were satisfied that cultivators would find it out in time. We knew it was useless to offer any advice upon the subject, as it would be considered quite gratuitous. To tell a man that a budded or grafted stock was worth double the price of a root-grafted one, would only create a laugh at our expense. We therefore thought it best to let those who estimate the value of a tree by its cheapness try the experiment fully and realize the truth of the adage,' a fool and his money,'" etc.

Mr. Hovey has been at length induced to say this, even at the hazard of being laughed at, on account of the objection raised against root-grafting in Illinois. But will Mr. Hovey be kind enough to explain to his readers wherein the superiority of budded or stock-grafted trees lies? We are all seeking light, and it is not enough to tell us we have been fools to throw away our money on root-grafted trees, but we must be told why. Will he point to the orchards of Western New York, where there are the most ample illustrations of root-grafting to be found in the world, we are very sure ? Will he point to the apple nurseries of Western New York, in which there are at this moment millions of root-grafted apple trees ? He will find no proofs to suit him here. The apple nurseries and orchards of New York, root-grafted as they nearly all are, are generally regarded as equal, if not superior, to any others in this country. We think Mr. Hovey has himself spoken very favorably of the orchards of New York. At any rate we should be glad to know where there are batter orchards, owing their superiority to budding or stock-grafting.