The opinion that trees, vegetables, and cereal grains do not succeed when planted more than once on the same piece of land in immediate succession, has its foundation in experience; and the advantages derived from a close adherence to the rotation system, whether in the garden or on the farm, is so evident as to need no defence; and when it is not in some measure fallowed, failure and disappointment are the inevitable results. But while this is true, it seems as if the injurious effects which flow from pursuing an opposite course, had in some instances been overstated, and reasons assigned which, to say the least, are unsatisfactory.

It has been affirmed, for example, that "wheat will not succeed after wheat, dahlias after dahlias, even by manuring the ground;" whereas wheat has been often grown in this way without disappointment; and dahlias have been planted on the same land four years in immediate succession, and, what is noteworthy, they grew better and produced finer flowers the last year than they did the first. Every gardener knows that onions can be grown on the same land for a series of years without any sensible diminution of crop. Still it is admitted such examples may be exceptional, and insufficient to prevent any one from following the alternate method of raising crops.

What is true of the Garden and the Farm, is also true of Fruit and Forest Trees, and abundant evidence could be adduced to show that by planting any of those in immediate succession, they do not succeed well. One remarkable instance of this came under my observation some years ago. A gentleman in the neighborhood of where I lived owned an extensive plantation of old trees, consisting chiefly of Scotch Fir and Norway Spruce; these were cut down, and shortly after the land was again planted, as well as an additional breadth which had previously been under wood. The consequences were, the young trees on the site of the old plantation died by the thousand, while those on the additional piece did as well as could be wished. At the time the old trees were cut, they were mostly sound and growing rapidly, and many bidding fair to equal those famed of old, "Hewn on Norwegian hills, to be the masts Of tome great admiral"

Apple, Pear, and Plum-trees have often failed when planted in a similar way, and it is more than likely that the cause or causes, in every instance, had been the same. How to account for such failures seems no easy task, and yet some facts can be stated which tend in some measure to remove the difficulties that stand in the way of rightly understanding their cause.

The opinion is entertained by some, and, indeed, such a one was expressed by an eminent fruit-grower before the Scientific Convention in this city some time ago. It was stated that "the Apple and the Pear did not succeed after the Apple and the Pear, because the first time had exhausted the land of those elements necessary for their growth." Now there can not be a doubt but that all trees exhaust the land in which they grow to a certain extent; but do they exhaust it so much as to account for the succession trees refusing to grow at all, or, in some instances, lingering in a weak and diseased condition? That such a proposition is insufficient to account for the failure of the forest trees stated above, is evident from the fact that they were in the high noon of their prime, and certainly taxing the capabilities of the soil greatly more than what the saplings, their successors, did or could do. If the land was incapable of supporting the young trees, how account for its ability to sustain the old? For the sake of illustration, take the case of the Cedars of Lebanon. Speaking of those trees, M. Lamartine, in 1832, says, "These trees diminish in every succeeding age. Travellers formerly counted thirty or forty; more recently seventeen; more recently still, only twelve.

There are now but seven. These, however, from their size and general appearance, may be fairly presumed to have existed in Biblical times"' It is according to analogy to suppose that had those trees been cut down any time during the last thousand years, and the same sort, or any of their congeners, planted instead, they would not have succeeded any more than those already referred to; and, besides, if such failures are attributable to the exhaustion of the soil, then we are forced to the conclusion that it takes a Cedar tree more than a thousand years to accomplish that which a Turnip or a Beet can do in one.

The only rational way of accounting for such phenomena is, to refer to the agency of fungous matter in the ground consequent upon the decomposing roots and old tree stumps. That such matter is present in cases of failure is exceedingly probable, and the roots of the young trees in its neighborhood, or in immediate contact with it, are likely to become diseased and finally perish. Should there be any doubts about fungi in the first stage of development poisoning the roots of trees, there can not be any when in more advanced stages; as the mycelium or spawn, which consists of elongated cells, often tangled and web-like, can be seen without the aid of glass or microscope, spreading over and destroying the roots of growing plants. The opinion seems to be generally entertained that such fungi grows only upon putrescent substances and the tissues of decaying roots. In its normal condition it may be so; still it is not singular to see the mycelium attached to roots still alive. The observing gardener may see many of the injurious effects of those subterranean enemies of vegetation, as they affect many of the crops under his care.

Its blighting influence may especially be seen in strawberry-beds, when by mistake they have been mulched with spent tanner's bark, saw-dust, or chips of wood.

To be practical, as regards the planting of young trees on the site of old orchards, the only remedy which can be recommended is, that care should be taken to remove every old root; and that can be done only by trenching the land as deep as the roots of the old trees had descended; or, as a matter of economy, it may be trench-plowed. Whichsoever method is adopted, it ought to be thoroughly done. The roots, as they are gathered, as well as the branches of the old trees, should be preserved for the purpose of burning on the land: and while doing this, as much of the land itself should be burnt as can conveniently be done. This, with the ashes of the wood, and bits of charcoal, make an excellent compost, which should be thoroughly worked into the ground as deep as it has been plowed or trenched, as well as a sufficient quantity of well-rotted manure. Should these conditions be complied with, the consequences would be, the land, which some might consider exhausted, would be restored to its pristine purity and productiveness.

[The above is an interesting topic; and while we agree with Mr. V. in regard to the mode of overcoming the evil, the common theory on the subject by no means accords with our own views. - Ed].