HORTICULTURISTS have within the last few years had a most formidable addition to the host of foes with which they have to grapple in the successful cultivation of the Grape-Vine. And it is scarcely possible to conceive of a more insidious and destructive enemy than the new invader - Phylloxera vastatrix - is proving itself to be. Any who have had an opportunity of watching the destructive power of this tiny insect, will not be at all surprised to know that the French Government are so alarmed at its appearance that they have offered a reward of a million francs to any person who will devise a means of destroying the pest, without, at the same time, destroying the Vines - especially when the enormous interest that France has at stake in her vineyards is taken into consideration. According to the report of E. L. Beck-with, Esq., on the Vines of the Universal Exhibition at Paris in 1868, the quantity of wine manufactured annually in France amounts to 831,000,000 gallons, exclusive of 165,000,000 distilled into brandy.

Taking this enormous quantity at the very low average rate of 2s. 6d. per gallon, it can easily be understood why France is so much concerned and dismayed at the progress of a foe which perils the very existence of her vineyards, and how this army of insects threatens to be a more formidable foe, in a pecuniary sense, than the squadrons of the German Emperor. It is already committing alarming ravages in some of the wine departments of France, and has spread into Spain, Portugal, and Austria.

About eight years ago the Phylloxera unfortunately made itself known in this country, and has proved fatal to the Vines in some English vineries, crossed the Channel to Ireland and the Borders to Scotland. We have recently heard of its fatal effects in a good many of the English counties. We have no conclusive proof up to this time that it exists in any place in Scotland except Drumlanrig, although we have heard of the Vines in several places in Scotland having in some cases died outright, and in others being curiously affected. Though such circumstances are suspicious, it can only be hoped that it is not the result of Phylloxera.

After the most careful observation, we have come to the conclusion that there does not exist in British gardens another insect that can be compared to Phylloxera, in the rapidity and certainty with which its work of destruction, in the case of the Vine, is carried on, nor one that is so difficult to combat successfully without the most prompt and ultra means. And in the interest of British Grape-growing, all who ( have any knowledge or experience of this destroyer should proclaim its whereabouts, and record their experience and observations; and at the same time, and above all, give it no quarter by risking its existence by any half-measures, but remorselessly stamp it out as the most formidable pest that ever found its way into a vinery. Indeed, we do not know that it is not a matter quite worthy of being dealt with as the rinderpest in cattle has been dealt with by the powers that be.

It will be in the recollection of many of our readers, that in the Gardener' of 18G9 (page 202), illustrations of this insect are given, and a paper which originally appeared from the pen of M. J. E. Planchon in the 'Comptes-Bendus de l'lnstitut' is translated. The history and habits, as far as then known, of the pest, are there minutely described.

Regarding the appearance of the insect, and the rapidity with which it multiplies and devours its prey, the writer's observations are correct; but we differ to some extent on the theory which he propounds as to its mode of attack. We refer to the article in question for the entomology of this little devourer, and will now detail some of our observations as to its effects, its mode of attack, and circumstances which favour its spread, etc. We may here state that not one of the observations to which we refer has been intrusted only to one pair of eyes, and that all that will be related has been corroborated by two and sometimes more observers. The insect is so minute - less than a cheese-mite - that all observations have to be microscopic.

The first warning that some evil was present in a vinery erected in the autumn of 1869, and planted in 1870, was, that two Vines at the end of the house, and that grew with great and satisfactory vigour all through 1870 and up to the midsummer of 1871, soon after the latter date began to flag. The leaves got prematurely yellow, and dropped off. Not for a moment suspecting the real cause, we were much puzzled at the occurrence, it being entirely new in our experience. But as the effect was so limited in its extent, and the two Vines being supernumeraries, and being heavily cropped, the impression wore off, and no minute investigation took place. In the spring of 1872, most of the supernumeraries that bore heavily in 1871 were removed, and the whole of the permanent Vines from one end of the house to the other broke with equal vigour, every shoot being literally packed at their points with fruit. All seemed to go right till the young growths were about 3 inches long, and the stored-up sap was exhausted. Then all the Vines at one end of the vinery, extending to the middle of it, called a halt, and those at the opposite end bounded on their way, running out their bunches as might have been expected. The affected half " spindled" like straws, and the bunches never ran out properly.

The roots were of course instantly examined, and all the most fibry and active parts of them were found in a peculiar half-dead-looking condition. Not even then suspecting Phylloxera as a cause, the occurrence was a puzzle, and some application was suspected, though I knew of nothing but pure river-water and a little soap that had been used in washing the woodwork and glass. Notches or incisions were then cut in the boles of the Vines, above the surface of the soil, and a little fresh loam put round them. There they soon emitted strong bunches of roots, and they made a tremendous struggle for life, and sent their leaders to the top of a long rafter, but woefully weak compared to those at the other end of the house, and the bunches were like black currants comparatively.