For some few years I have amused myself by forming my Plum trees into pyramids, feeling convinced that no other mode of cultivating our hardy fruits is so eligible for small gardens. I was induced to take extra pains, on account of observing that our neighbors the French, so famous in their cultivation of pyramids, failed to a certain extent with the Plum; as their trees, I observed, on being pruned to that shape made too vigorous shoots, and were inclined to gum. They do not know the value of root-pruning, and will not listen to it; I do, and therefore felt some hope of success. At first I commenced to root-prune once in two or three years, but I soon found that was not enough, for the Plum makes roots so rapidly that it is difficult to check it; I have now, therefore, for the last three years root-pruned annually, early in autumn. My success is perfect; this I have generally done in September, soon after gathering the fruit, but this year not having any fruit, and awakened by your article on "Summer Root-Pruning," given in Gardener's Chronicle in July, I operated on them in August; the trees almost immediately went to rest,and are now pictures of forthcoming fruit-fulness. The operation is so simple, that any one may exercise it without any fear of failure.

Let me attempt to describe it; and yet how irksome it is to have to employ so many words about what one can tell and do in a few minutes. Open a circular trench, 18 inches deep (for the

18 inches from its stem; for the first two or three years this distance will be enough: increase the diameter of the circle as years roll on, but very slowly, not more than from 1 to 2 inches in a year, and cut off every root and fibre with a sharp knife. This operation may be likened to the manner in which old folks talk of the way in which they used to cut the hair of poor workhouse boys, viz., place a basin on the boy's head and trim off the hair round its rim - in short, the "Workhouse cut;" then when your roots are so trimmed, introduce a spade under one side of the tree and heave it over, so as not to leave a single tap root. Fill in the mould; if the weather is dry give the tree a soaking of water, and it is finished. If your soil is poor, give a top-dressing of manure, to be washed in by winter rains. The following summer pinch off the ends, in June, of any shoots that seem inclined to push more than 4 inches, and thin those out with the knife that are too crowded: the result will be a handsome and highly prolific pyramidal tree.

Plums are not yet half appreciated; for. owing to the introduction of many new ana good varieties, they are in season from July till November, for the dessert and for the kitchen. - lb. conjectures as to the mode in which the Earth was originally clothed with Plants. - It is an interesting question to determine the mode in which the various species and tribes of plants were originally scattered over the globe. Various hypothesis have been advanced on the subject. Linnaeus entertained the opinion that there was at first only one primitive center of vegetation, from which plants were distributed over the globe. Some, avoiding all discussions and difficulties, suppose that plants were produced at first in the localities where they are now seen vegetating. Others think that each species of plant originated in, and was diffused from, a single primitive center, and that there were numerous such centers situated in different parts of the world, each center being the sent of a particular number of species. They thus admit great vegetable migrations similar to those of the human races.

Those who adopt the latter view, recognise in the distribution of plants some of the last revolutions of our planet; and the action of numerous and varied forces which impede or favor the dissemination of vegetables in the present day. They endeavor to ascertain the primitive Flora of countries, and to trace the vegetable migrations which have taken place. Daubeny says, that analogy favors the supposition that each species of plant was originally formed In some particular locality, whence it spread itself gradually over a certain area, rather than that the earth was at once, by the flat of the Almighty, covered with vegetation in the manner we at present behold it. The human race rose from a single pair, and the distribution of plants and animals over a certain definite area, would law. Analogy would lead as to believe that the extension of species over the earth originally took place on the same plan on which it is conducted at present, when a new island starts up in the midst of the ocean, produced either by a coral reef or a volcano. In these cases, the whole surface is not at once overspread with plants, but a gradual progress of vegetation is traced from the accidental introduction of a single seed, perhaps of each species, wafted by winds, or floated by the currents.

The remarkable limitation of certain species to single spots on the globe, seems to favor the supposition of specific centers. Professor E. Forbes says, the hypothesis of the descent of all the individuals of a species, either from a first pair, or from a single individual, and the consequent theory of specific centers being assumed, the isolation of assemblages of individuals from their centers, and the existence of endemic or very local plants, remain to be accounted for. Natural transport, the agency of the sea, rivers, and winds and carriage by animals, or through the agency of man, are insufficient means in the majority of cases. It is usual to say, that the presence of many plants is determined by soil or climate, as the case may be; but if such plants be found in areas disconnected from their centers by considerable intervals, some other cause than the mere influence of soil or climate must be sought to account for their presence. This cause he proposes to seek in an ancient connection of the outposts or isolated areas with the original centers, and the subsequent isolation of the former through geological changes and events, especially those dependent on the elevation and depression of land.

Selecting the Flora of the British Islands for a first illustration of this view, Professor Forbes calls attention to the fact, well known to botanists, of certain species of flowering plants being found indigenous in portions of that area, at a great distance from the near assemblages of individuals of the same species in countries beyond it. Thus, many plants peculiar in the British Flora to the west of Ireland, have the nearest portion of their specific centers in the north-west of Spain; others, confined with us to the south-west promontory of England, are, beyond our shores, found in the Channel Isles and the opposite coast of France; the vegetation of the south-east of England is that of the opposite part of the continent; and the alpine vegetation of Wales and Scotch Highlands is intimately related to that of the Norwegian Alps. The great mass of the British Flora has its most intimate relations with that of Germany. He believes, therefore, that these isolated outposts were formerly connected together by chains of land, and that they have been separated by certain geological convul