Paulownia imperialis. - This is a magnificent tree, of recent introduction. To all appearances it will not grow to a very large size in our climate. As it is perfectly hardy it will be a rich addition to our collection for the shrubbery or lawn. We have not yet seen the flowers. We planted a number of trees three years since, which endured the two last winters to perfection. These trees were not pruned, but the branches were permitted to strike out near the ground for the purpose of layering. As they now appear, they would be ornamental in the shrubbery, even without bloom, on account of their showy foliage. Mr. Downing has given us a description of this tree, in the Horticulturist, and we will give his full and interesting description of it as we find it in vol. i., page 16 :"The striking peculiarity of the Paulownia, however, is its showy foliage. The leaves are the shape of those of the Ca-talpa, but of a darker green, perhaps resembling more closely those of a large Sun-flower - being broad and heart-shaped. In rich soil the growth of the tree is extremely rapid - young plants making shoots of eight or ten feet in a season, and on such we have measured leaves a foot and a half in diameter. But on older trees they are usually about half that size.

"The flowers are produced in April, in panicles, at the ends of the branches. They resemble in general appearance those of the Catalpa, but the color is a pale-bluish violet."The seeds are borne in an oval capsule as large as a pigeon's egg.

"When the Paulownia was first introduced into the Garden of Plants, at Paris, it was treated as a delicate green-house plant. It was soon found, however, that it was perfectly hardy on the Continent and in England. In this country, it appears equally so. The trees in this latitude have stood the past two winters, even in exposed situations, without covering, and have not lost an inch of the previous season's growth. We, therefore, consider it a hardier tree than the Catalpa, which often suffers badly from the cold of this latitude. Nothing is easier than the propagation of this tree. Single buds will grow, like those of the Mulberry and the Vine, taken off early in the spring, and covered about an inch deep in the soil of a fresh hot-bed. The cuttings of the young shoots, planted under a hand-glass in a shady border, strike root readily. But by far the easiest and most rapid mode is that of planting pieces of the roots.

"Every little piece of the root of the Paulownia will, under certain conditions, produce a plant. It is only necessary to make a common hot-bed early in the spring, reduce the roots of the parent tree, (and it will bear a very severe reduction,) and plant every piece that will make a cutting not smaller than a goose-quill, and a couple of inches long. Plant these bits of roots about an inch and a half deep in the rich, light soil of the hot-bed. In a fortnight's time every bit will throw up a bud, make new roots, and become a distinct plant. When the plants are about three inches high, they may be transplanted into rows, beds, borders, or, in short, wherever they are finally to grow. If the season is favorable, they will grow to the height of from three to six feet before the close of the autumn. Next year, if the soil is deep, they will make shoots eight or ten feet long.

"When the Paulownia was first offered for sale in Europe, about three years ago, it was advertised by the Brothers Bau-mann, the great nurserymen of the Rhine, at from three to six guineas per plant. From the rapidity with- which the nurserymen are propagating it now, in this country, we have no doubt it may be bought next autumn, at wholesale, at about the same price per hundred trees.

"The parent tree, in the Jardin des Plantes, Paris, has already borne seeds, in considerable quantity, which have vegetated very regularly. The tree has not yet, to our knowledge, flowered in this country, but will probably do so next spring. As soon as the seeds are produced in abundance, we advise.cul-tivators to resort to them - the best of all modes of propagating ornamental trees - when it is possible to do so."