Mr. Henry Lawrance, a cotton merchant, is the horticulturist of New Orleans. Mr. L. originated the Crescent Seedling Strawberry, which has not succeeded at the North, but, he assures us, retains all the characteristics claimed for it in this climate. The fruit was just coming to maturity, and was bringing monstrous prices in the stores on Canal Street Mr. L. kindly drove us to his fine garden residence, now almost, if not quite, within the built part of the city. The Crescent Seedling bush is apparently a smallish one, with only a few leaves above ground; yet the berries were very numerous and showy, but not, to a Northern eye, very large.

At Mr. Lawrance'8 we again felt for Northern cultivators who were now (March 31) employed in shovelling snow, while Mr. L.'s garden was most superbly ornamented with orange, lemon, and lime-trees, in full bearing. His foreign grapes (in the open air) are moderately successful, though, we presume, the atmosphere is too damp, as a general thing. He has success with the banana when planted on the southern side of a house. His bees and poultry are remarkably fine, and we could not but envy some of his successes.

As a general thing, gardening about New Orleans is net much studied. Efforts are being made to get up a horticultural society, and Mr. Lawrance has moved in the matter, and interested some of the influential and wealthy citizens; but the town is so much occupied, in winter, by transient residents seeking a fortune, and, when that is acquired, leaving for their native places, that it requires great exertion to do a good thing for general benefit. The place, too, is so constantly and easily supplied from two regions by steam - the tropics and the cereal or apple country above - that there seems less inducement to cultivate on the spot what nature appears to have designed to bring to their doors at so little cost. Nevertheless, a society will be very Useful, and we were very glad to hear Dr. Mercer (the Girard of New Orleans) express his willingness to assist, and his interest in the matter. Mr. Lawrance, we were glad to see, had supplied Dr. M.'s table with an early basket of Crescent Seedlings.

We could hear of but few good public gardens, and after a saunter among the beauties of the suburban villas of Lafayette, where more variety of planting might be studied With advantage, we finished our view of New Orleans by a visit to its cemeteries. They present the novelty to Americans of entering in tombs and ovens above ground; but, altogether, there was more neatness, and less to object to, than we had been led to expect. Expensive monuments are general in the best grounds; we could but copy from one the following most touching inscription: -

" There is sot an hour . Of day, or dreaming night, bat I am with thee;

There's not a breeze but whispers of thy name,

And not a flower that sleeps beneath the moon

But in its hues and fragrance tells a tale of thee,

Poor Caroline Only 23.

Dearly loved, and deeply mourned, by one faithful heart".

There is but one inscription, which we now call to mind, that has impressed us so forcibly in reading on the spot; it is that of Gray, the poet, to his parent, in the churchyard 6f his own elegy, at Stoke Park, the residence of the Penn family: -

"The mother of many children, One only of whom had the misfortune to survive her".

Not meeting the friend to whom oar visit was principally intended, we left the elegant hospitality of New Orleans, and joined him, by telegraphic invitation, at Natchez (Mississippi), ascending the river in the fine steamer Princess, built to accommodate the better class of passengers from Memphis and Natchez. Every comfort that seems practicable, is combined in this boat; the sleeping arrangements are eminently comfortable; the table all that could be desired, each day furnishing the luxuries which we had brought in the Empire City from Havana, of bananas, oranges, and even pine-apples. So far has the luxury of these river boats been carried, that a St. Louis packet, the New World, now sails equipped with the force and material of a dotty paper on board, and with a job office attached for printing the bills of fare, and other work. This was to be one of the novelties of the Leviathan, but Brother Jonathan is in advance of the English in these matters.

The upper deck cabin of the Princess is two hundred and eighty feet long; when well lighted up with Cornelius' Philadelphia lamps, it is one of the most striking scenes imaginable. We ascended rapidly through the sugar region, and entered upon that of cotton before reaching Natchez. This sugar country presents many attractions; more cultivation and thicker settlements than we anticipated. We could distinguish as a frequent tree, the Pecan, which is somewhat like a hickory, and produces most abundantly; the inhabitants here away, however, pay little attention to supplying anything but sugar. The best pecans come now from Texas.

The progress of the boat was stopped occasionally, to run its bow into a bank, and laud a few passengers or cotton baling; the cotton, and the food for the negroes, is a descending cargo on this river. Occasionally, very large and showy houses and out-buildings came into view in this level country, marking the residences of successful sugar growers, and sometimes a good, shady garden, with its golden orange-trees, marked the scene. On the spots most adapted to sugar, there appeared to be an amount of very comfortable housekeeping, but we never shall get accustomed to a river that is always pouring itself out, and running one way! This is, no doubt, prejudice.

The great rivers emptying into the Mississippi, it might be naturally expected, would present some kind of improvement at the junctions; but rarely do we find this to be the case. At Bed River, we stopped to dismiss two passengers, and moored alongside a " shore boat," the only habitation visible. These boats are mere waiting places, and are about as comfortless as possible.

Natchez reached, our first visit was paid to the great plantation of Dr. Mercer, Laurel Hill. The road, of some ten miles, passes many fine plantations and excellent houses; among others, that of Mr. Sargent, one of the Boston family of that name, who was Commissioner to receive Louisiana into the Union on its purchase. Here began to be visible the miles upon miles of hedges of the Cherokee Rose, which, we must say, is one of the most beautiful objects of the kind ever presented to the eye. It was in full bloom - the leaves of dazzling brilliancy, and the coming buds most vigorous and graceful. These hedges occupy the great breadth of ten feet, and fall about in regular festoons of exquisite beauty, which no description can bring vividly to the reader. What a pity this rose is not hardy north of the Carolinas!

But if the hedges were so magnificent, what was the Northern lover of trees to say to the evergreen magnolias, M. grandiflora, which soon became as common as our oaks in the forests? Thousands lined the road in every coppice with their glorious dark foliage, and of dimensions like our tulip-trees. This experience of hedges and magnolias alone compensated for all our fatigues. Sometimes the Cherokee Rose festooned the magnolia, a sight we hope never to forget. On entering Dr. Mercer's park and woods of four thousand five hundred acres, these trees became giants; intermixed with oaks, the contrast was lovely beyond our powers of description. Dr. M.'s house is occupied by an adopted son, Mr. Shields, whose hospitality deserves more than a note; it is built to suit a Southern climate, and might be likened somewhat to a first class East India bungalow, enriched with every elegance. Built round a hollow square, and of one story, it presents an appearance of comfort such as one would select to repose in for a few centuries, if the lease of life were to be so extended.

Its verandas and projecting shades exhibit on every side the finest old trees of evergreen magnolias, casting their dark green shadows on the lawns; these, and the fine oaks, record their planting by nature's hand long anterior to the occupation of the white man; they would be the pride of the oldest family in Christendom. Their enormous stems were covered with running vines, while the limbs of one magnolia we paced, extended in a circle of three hundred feet I As we drove through the park, an occasional whirr marked the rising of a wild turkey; so completely is the scene one of nature's own glorious formation, that we wished all our readers could enjoy it with us. The Bignonia capriolata here grows wild, and festoons itself from the highest limbs.

In the garden (ably controlled by the ladies of the mansion), the Camellia lives in the open air, and attains a height of fifteen feet. Pomegranites require no housing, but issue a succession of scarlet flowers and excellent fruit. But what shall we say of the roses f A white Lady Banks Rose we took the pains to measure; the stem, at three inches from the ground, is twenty-one inches in circumference, and it covers a circuit of ninety feet, running, and hanging full of bloom from every tree within its teach, to the height of thirty or more feet! Hedges of Pyrus japonica, Magnolia purpurea (eighteen feet high), Wax-trees (Ligustrum lucidum), Crape Myrtles (Lagerstroemia), twenty-five feet in height, Coral plants, Pittisporums, and similar greenhouse pets with us, run riot in this delicious climate. The finest red roses mounted the pine-trees to the upper branches, forty feet from the ground. Moss roses, the Olea fragrans, white Tea roses (whose bloom measured eleven inches in circumference), peaches, pears, and so forth, were as numerous and superb as heart could.wish. Grapes do not succeed very well.

Dr. Mercer possesses eight thousand acres here, less than one-half being a cotton plantation, occupying four hundred and seventy hands. When we say that we dined on asparagus and strawberries at this early date (April 3), we must leave the reader to imagine the rest.