bark, and so affect it as to occasion an unnatural and excessive development, a corky, irregular, warty growth, which finally bursts the outer cuticle, and covers the infested branches with unsightly excrescences. To this latter group belongs the Sphaeria morbosa. The fleshy growth which it induces in the plum-tree, or at least that portion which is immediately occupied by it, is called its stroma. This is, at first, a homogeneous mass, presenting no definite character. By and by, it takes on a reddish coloration, which finally deepens into black; the surface becomes carbonaceous in texture, and is studded all over with minute papillæ. A section of the stroma will then exhibit a woody centre with a carbonaceous rind. In this rind are innumerable little rounded cavities, the upper walls of which constitute the before-mentioned papillæ : these are pierced by a minute hole, through which the spores, or germinating processes, escape; the whole cavity and its walls being called a perithecium. The spores are infinitesimally minute, oblong bodies, contained, generally eight in number, in diaphanous sacs, or envelopes, called asci, which develop from the ends of filaments, which line, in a dense mass, the whole bottom and sides of the cavities. These are not carbonaceous like the walls, but are of a gelatinous consistency. Imagine an egg-shell, from the inner walls of which grows a dense mass of soft bristles half an inch long, on the ends of which are little whitish, sausage-shaped sacs, containing oval bodies lying diagonally in the sacs, one applied to the other, sidewise, the bodies being variously lined, and you have a tolerable idea of an immensely-magnified perithecium, with its filaments, asci, and spores.

That this structure we have just described should be a plant; that this hard, black, charcoal-like substance should be vegetable,—will seem strange to those unfamiliar with the study of similar growths; but it is vegetable, and has so permanent a character as to constitute a species. It must be allowed, however, that it is a matter of doubt, in mycology, how far the same fungus may be affected by the plants upon which it fastens as to change its habits and appearance. The older mycologists named the host of parasitic fungi after the plants upon which they were found; taking it for granted that they were all distinct species if they had a different look. Schweinitz, the great pioneer of the study in this country, has enumerated a vast quantity of them in this way; but, since later observations have

proved that many fungi take on different growths under varying circumstances, it has become a matter of considerable question how far the autonomy of these obscure vegetable growths can be established.

The group to which this particular fungus belongs, is, however, tolerably constant in character. The genus Sphaeria is well defined, if we include the newer genera made out of the old genus by later writers, more for the convenience of treating of so vast a number of species, it seems to us, than on account of difference worthy of generic distinction. These carbonaceous papillate fungi are so well defined in their peculiarities as to be readily identified by those familiar with their forms. Yet even these vary; and, when closely proximate forms are found on different plants, a question arises whether they are identical or not. The young growths of the wildcherry (Cerasus serotina) are often found covered with a fungus very similar to the Sphaeria morbosa. Indeed, almost any woodland border will furnish plenty of specimens. The perithecia are smaller, and are sometimes prolonged into a short beak. The cherry belongs to the same order as the plum; and it may be that the parasitic fungus infests both, but is swayed by influences in both plants so as to develop differently. We have seen branches of the cultivated cherry similarly affected. The size of the spores is considered a good specific character, and yet these vary.

It has been thought by some that the peculiar growth of the bark which bears this fungus is occasioned by the sting of a curculio; but any one familiar with the stroma of fungi will understand that this growth is characteristic of a whole family, and arises, not from insect poisoning, but from fungus influence. The insects, seduced by its soft, pulpy character in its early stages, may deposit there their eggs, as it is not unlike the flesh of unripe fruit in texture, at one period. Various methods have been devised to stay the ravages of this fungus. Sulphur placed in holes made in the trunk of the tree has been resorted to; but we imagine that there are no sure preventives. When we remember the excessively minute size of the spores, we can understand that they may be absorbed with the nutriment of the tree, or taken into the stomata of the leaves, and carried into its tissues. Fungi infest wild plants as commonly as cultivated ones; a proof that their occurrence is not necessarily due to an unnatural or deteriorated state of the plant they attack. Charles F. Sprague.

BOSTON, February, 1867.

GARDEN ARCHITECTURE, AND HINTS ON LANDSCAPE GARDENING.

IN treating of architectural gardening, it may be expected, that, at the commencement, some allusion should be made to the general principles of design.

The principles governing all design are UNITY, that is to say breadth, and INTRICACY, that is to say variety, including contrast. The former governs the whole scope of the design: the latter supplies the details. The influence of the one may be seen in works distinguished by their GRANDEUR and REPOSE; the charm of the latter, in the combinations which produce PICTURESQUENESS and CHEERFULNESS.

To know exactly how far to allow either breadth or variety to give its especial character to a composition is the great secret of successful design. There must be a proportion, and yet a preponderance; enough breadth to secure repose, enough variety to insure interest without creating confusion. In short, breadth must be so produced as to allow the aid of variety; while variety itself, to be pleasing, should be treated in a broad

manner.

A few diagrams will serve to show how the principle of breadth applies to garden design, including the architectural features of terraces, which are introduced, not as garden architecture, but simply for the purpose of illustrating principles.

If any reader should have difficulty in understanding what, after all, is really meant by breadth, let him look out of a closed French casement at any object whatever, taking care to place himself opposite the centre of the window: he will then see the view cut into halves; or, in other words, that all breadth is destroyed. He will not know on which half of the view to fix his attention, and will instinctively change his position until he sees without obstruction all he desires.

It may seem paradoxical, but it is none the less true, that, under certain conditions, breadth may be destroyed by the very absence of a central object.

The following diagrams, 1 to 12, will show the application of the principle of unity, or breadth, to garden compositions :

In Fig. 1, we have a fair expression of unity. The grass in centre is bordered by trees or shrubs. But the grass-flat is the feature to which the walks at the sides are entirely subordinate; and whether this grass-flat be cut into beds, or whether the flat is composed entirely of gravel and beds, is immaterial.

Fig. 2 expresses unity, perhaps, more plainly than Fig. 1. consists of a path bordered by turf, flowers, shrubs, or trees.

The centre

Fig. 3 will be seen, on examination, to be identical in principle with Figs. 1 and 2; that is to say, the garden in Fig. 3 is not in two halves nor in four quarters, but one central whole, bounded by an enclosing border of flowers, shrubs, or trees.

Fig. 5 is not so good as Fig. 3. It somewhat resembles Fig. 4 in having the object, namely, the central grass-flat, in the centre of the view. If the central grass-flat were treated differently from the rest by sinking a tolera

Fig. 5.

bly deep panel, or filling such a sunk panel with water, the effect would be pleasing.

As balustrades with flights of steps, vases, &c., form the chief part of the architectural decorations of a garden, this is the proper place to show that breadth of treatment applies to them in the same manner as to the main divisions of a garden or view. It will be seen, for instance, that the objectionable feature represented in Fig. 4 is reproduced in an architectural form in Fig. 7,—namely, the pier in the centre of the view; not important enough to awake interest, but sufficiently obtrusive to produce confusion. It may be safely taken as a rule, that a pier should never occupy the centre of any wall, space, or balustrade, but invariably an opening, or void. We should either look at one object of sufficient importance, or between two at a third more distant.