[Read before the Germantown Horticultural Society.]

The question as to what are the three best street trees, and as to trimming in cities and towns, is as interesting as it is broad. It is a curious fact that if we examine the writings of the greatest lovers of trees, we find almost no allusion to the trimming process except in forest culture, because probably they do not approve of mutilating their pets. The art, if there be any such, should consist in trusting much to nature. Begin early with the business, first having a decided design as to what the tree shall become. Remove the branches that are superfluous, or likely to become so, while young, when no injury will result. Take example from the fruit grower, who forms his pear tree into a pyramidal or a fan shape; in short, who plans to have, and does have, just what he desires. If he wishes to spread the limbs on an espalier, he finds no difficulty whatever in doing so. We can treat a street tree in the same manner, but we must know what is required, and give constant attention to the detail as the limbs progress.

This, and this only, will prevent the necessity for mutilation when the branches have attained too great height or are too numerous.

Watch and learn the proceedings of an accomplished fruit raiser. Who will do this? it may be asked. It is feared the numbers will be few, but without care of this kind, the rapid-growing specimens will often have to be cut, most probably mangled, disfigured and killed. This society would do a good service by recommending a person with the requisite knowledge, and the probability is, that our fellow citizens would - some of them, at least employ him. In a few years his results would be an example that would educate others. Trees of quick growth in towns with narrow streets require more or less trimming; it is in vain to disclaim against the "vandals" of the saw and hatchet, till some degree of education is instilled into the masses. It-is equally in vain to have handsome, quick-grow-ing trees, such as most persons desire, without some attention. We should rather condemn the owner who neglects his trees, than cast aspersions at the man, however ignorant, who obeys orders, and in whose power it is not to reduce an overgrown specimen without using his rough tools.

What are the three best trees to plant in streets at the North, is a question attended with some difficulty, because, notwithstanding the use, the grandeur and the beauty of timber trees, it is a fact that, compared with herbaceous vegetables, the number of species distributed over the world is comparatively small. The greater part belong to warm climates, for in the temperate zones, and in the regions of warm countries rendered temperate by their elevation, the number of genera of timber trees, according to the best authorities, that attain thirty feet in height, does not amount to a hundred. There are not above a dozen genera of trees, furnishing in all about thirty species, which attain that height, indigenous to Great Britain. Other countries, however, furnish other genera and species from which to select. These we have in considerable varieties. The choice is restricted most painfully when we consider the circumstances we are reduced to in the selection. We cannot properly have fruit or nut bearers, nor even flowering trees, with safety to our windows or our heads; for there is a species of curculio, called in Paris a gamin, whose great delight is to throw sticks and stones at everything that pleases his fancy or his palate.

We must therefore exclude from the usual streets our hickory, our walnut, our horse and native chestnuts, the honey locusts.(one of the most graceful of trees), and of course the apple, the pear, the paw-paw, and all fruit-producing trees. Then, again, we are restricted to what will flourish in cities and towns; evergreens will not succeed in smoky regions.

Then, again, consider the conditions which we are subjected to. Our streets are narrow, often only thirty feet wide. The space is insufficient for flourishing trees, and no sickly tree or plant is worth preserving. As well admire a sick monkey or a dying cat as a plant struggling for life between a curb stone on one side, sand, brick and rubbish on the other, and the air and rain excluded from all; and yet, strange to say, we do sometimes see that nature struggles against such unnatural obstacles, and gives us something to like, if not to admire, even though the planter may have failed to dig deep enough, or to supply pabulum for the root. The one tree which resists this confinement best is undoubtedly the silver maple; and if it were treated as I have suggested, and oared for in its rapid progress, it would be the tree for our purpose. As a single specimen on a large lawn, it assumes most of the characteristics we desire, if it has no near neighbor. It wants attention every week during the growing season if we expect good results. It throws up the pavement with its tuft of superficial young roots. The bricks must be removed, and the tuft cut away with an adze or some suitable implement.

Properly done, this does not injure the growth materially, the large roots being sufficient, and having penetrated the soil. Therefore, under the conditions named, I do not hesitate to recommend it as one of the three desirable street adornments where a better cannot be expected to grow. But if it is left for years without trimming, and thus is allowed to form tall and large limbs that must be cut away, mutilation in its worst form will result.

The sugar maple, however, should be preferred; and this or the red bud should be another of the three. The beautiful round-headed Norway maple casts too dense a shade for the street.

The magnolias must not be forgotten; the two should be the cordata and macrophylla, the first producing yellow flowers twice in the season.

I sometimes think I would rather inherit Mr. Magnol's reputation for the name of magnolia, so graceful and tripping, than that of Bonaparte; and then, how his family increases! He never knew he would have heirs called Soulangeana, etc.

The yellow wood, Virgilia lutes, affords a good variety also, when we consider what we shall select as our second choice. The deciduous -cypress becomes in time a beautiful and valuable street tree, while the Chinese cypress, Glyptostrobus sinensis lately introduced, is the most perfect of all pyramidal trees. We must also, by no means, forget the lindens.

And for the third, some of the oaks are to be chosen, while the Kentucky coffee tree, Gymnocladus Canadensis, has many valuable characteristics, and should be more frequently planted. And the varieties of the ash are admired by many very justly. The native beech, too, has advocates; while the true copper beech, when to be procured, would form a superb and unexceptionable ornament everywhere, especially in an avenue or on the street. The fern-leaved beech, Fagus hetero phylla, with conical form, well-defined outline, and deeply cut, close foliage, is superb and rare. The Salisburia, or ginko tree, should be introduced into our public plantings and even streets.

Objection is fairly made to the use, in this region, of the elm, so much admired in Eastern towns, because it is infested with worms; but the variety generally known as slippery elm, Ulmus fulva, has no enemies, is equally graceful and valuable, and should be cultivated extensively.

Some varieties of the ash family make good street trees, but after all we are often narrowed down to what we can get. The Acer 'The Horticulturist and Journal pseudo-plat anus, among the maples, is not so rapid growing as the silver, but more rapid than the Norway or sugar maple. Among the oaks, prefer the macrocarpa, which is a fast grower.

A knowledge of all the different associations which belong to each particular kind of tree, as it must add greatly to the enjoyment derivable from them, ought always to form a part of the pleasure with which trees are viewed. We have a pleasurable sensation of the mind when we pick up a chestnut, the ancestor of which was planted by Washington at Belmont. The association of ideas thus connected with trees has given rise to what is called their moral and historical expression, as the oak for ship building, the pine and fir for house carpentry, and so on. The historical and geographical associations connected with trees are numerous, and of great interest. The plata-nus reminds us of the respect paid to this tree in Persia; the sweet bay, of its shoots being used by the Romans to crown their warriors; the vine and the olive, of their unknown antiquity, and the highly prized liquors and oil made from their fruits; and the cedar of Lebanon, of the esteem in which its wood was held by Solomon.

That there are difficulties in selecting has already been demonstrated, and when these are all over, comes another. The best trees and the right sizes are not always to be had when wanted. There may be plenty of them, but they are small, possibly, or too large, and they may be very difficult to transplant, as the holly and many others are. Most persons don't want to be bothered, nor do they desire to plant twice or three times, and they, forsooth, content themselves with what is on hand; it is very apt to be the silver maple. As our country gets older, and we have more extensive nurseries, like Loddiges' in England, one can go thither and find exactly what is wanted, and in every stage of growth. It is not yet so in America.

The subject has been considered in one aspect only. What are the best trees for streets embraces a wider range as streets become wider, and enlarge into avenues of eighty or one hundred feet in width. Then our list for planting in good soil, unobstructed by curb stones and bricks, is immensely enlarged; and we can recommend the oaks, and hickories, too, perhaps the tulip poplar and many others; but confining the subject to the usual plan of streets as exhibited here, the range for selection is rather limited. In most instances it is well to get a guarantee from the nurseryman that his plants have been twice transplanted, otherwise there is a risk of some deaths. With twice transplanted trees there is little to apprehend with careful attention.