The Royal Horticultural Society formally inaugurated the opening of its new gardens at South Kensington on Wednesday, June 5, 1861. The occasion seems to have been one of peculiar interest, and was marked by all the eclat that could be given to it by speeches, processions, music, the presence of the royal family, and a very grand floral exhibition. We give below Mr. Beaton's very spirited account of the Exhibition. It will not only give our readers a good idea of what is said to have been the finest exhibition ever held in London, but the managers of our own exhibitions may gather useful hints from it. The following is Mr. Beaton's account, taken from the Cottage Gardener;

"This will be a memorial day in the annals of gardening. From the day Mr. Sabine took up the spade at Chiswick, to the planting of that Wellingtonia on the 5th inst. by the Prince Consort, immediately after he had opened the new Garden and declared it to be the inner court of a vast quadrangle of public buildings where science and art may find space for development, the science of our craft found small space for developing the energies of the practical mind of gardeners; and practically, we had no leader for the last forty years, otherwise we might have turned out more Paxtons, Mclntoshes, Flemings, and Elyes, and other heads of sections of the circle than we have done. But let us be thankful, and hope that the next forty years will make up the difference; and that the heads of the different branches of the cultivators of the science, and of the practical part of the work before us, will unite their efforts, not only within the ' vast quadrangle,' but extend them to the land's end on each side of it, and to the limits of the great circle whose products and properties we are all interested in developing.

"This commencement was on a magnificent scale, and every one, from the highest to the most humble, who contributed to the success of the opening scene, must have been well pleased at the result. All the arrangements were perfect, as far as I could see and hear. There never was such an enormous stock of plants in one place before, and of such a description. In twenty-three years after the first experiment was tried of showing plants for their own sake instead of for their flowers, two-thirds of this vast gathering were of that very description; and some of those who were the foremost to laugh at the daft experiment of 1838, were laughing in my presence in these arcades at their own good luck and success in crowning the rival to the floral fancy, and you never saw another set of people more in harmony and more pleased with each other than we were.

"The most extraordinary circumstance, however, connected with this step in the progress of our experiments, was a large collection of most welcome plants that were sent from Japan by Mr. Fortune expressly for this Exhibition. These Japan plants arrived in England on the Friday before the exhibition day, and were in a fit and proper state for the exhibition tables - in short, as good specimens of cultivation as ever I remember to have seen exhibited by English garden era in these very rare or very new plants. Indeed, I could name some plants at the Exhibition which came from within a short distance from the Garden, that were not so creditable to the growers as those sent over by Mr. Fortune were to the gardeners of Japan. These Japanese seem to have the very same style of taste in plants as ourselves, and also to have as good gardeners and as careful propagators as we could turn out. Mr. Standish, of Bagshot, exhibited these plants, and, of course, he will set to and propagate and sell them as fast as possible.

"Cyanophyllum magnificum and Dion edule were the two most splendid plants there. One plant of Acrophyllum venosum was the greatest triumph of gardening there in growing specimen plants; it was in a first-prize collection of nine plants by Mr. Chilman. The best single specimen there, or any where else in Europe, I should think, was Mr. Warner's Laelia purpurea with thirty-six fullblown flowers on it. It was only the week previous that I was boasting of one at the Crystal Palace from Mr. Stone, which had eleven blooms on; and even at this grand Exhibition, two of the best Laelia purpureas had each only eight flowers. The greatest success over the greatest difficulty in growing very rare plants, was Mr. Leach's exhibition of the Disa grandiflora, growing exactly like a luxuriant native along the edge of some ditch where there were no commissioners for looking after the drainage and sewerage.

" In my own favorite family of Ferns, Gleichenia is now the most favored at the Exhibition, and I think every species of it was there; and every one who showed Ferns had more or less of the different Gleichenias.

" The Fruit was most tempting, and the only part at the Exhibition that was not well arranged for. The fruit stand was an oversight - it was a double stand with one side, or one-half in the shade, and facing the back wall of the arcade; of course, one-half of the fruit could not be seen well. The Pines were as good as usual. The White Grapes not quite ripe enough for a high-class dessert; the Black Grapes were never better seen in this globe. The Buckland Sweetwater, for which I risked my liberty three years back at the Crystal Palace, was by far the best White Grape there, and will be the gardeners' best friend in White, as the Hamburgh has always been in Black. Ingram's Hardy Prolific Black Muscat is decidedly of the Black Prince section, and the very best of Grapes; and the Trentham Black is of the Hamburgh race, and wore the best bloom of all the Black Grapes there. But I must put off the best part of the fruit tale till I have more time and room, adding only this remark on the grand new idea of giving prizes for dessert arrangement - that it turned out exactly as some of my patrons, from whom I learn all about the fashions, colors, taste, fancy, and forget-me-nots, predicted to me months back; and I would be bound that nine out of every ten gardeners who saw these desserts in competition, did not understand even the meaning of the first-prize dessert.