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Summer (Fr globose indehiscent seven)

fr. globose, indehiscent, seven lines broad. l. 4in. long, oblong, acuminate, white-tomentose beneath. Branchlets covered with rusty-white tomentum. Sumatra. Stove. (B. M. Pl. 169.) S. californica (Californian). fl., pedicels with the calyx and corolla minutely canescent; style becoming 1in. long. fr. a bony seed, the size of a small cherry. l. oval, entire or sparingly undulate, 1in. to 2in. long, short-petioled. h. 5ft. to 8ft. California. A shrub with scurfy, stellular pubescence, at first hoary, sometimes soon green and glabrate. S. grandifolia (large-leaved).* fl. mostly in elongated racemes; corolla 1/3in. long, convolute-imbricate in bud. Spring. l. obovate, acute or pointed, 3in. to 6in. long, white-tomentose beneath. h. 6ft. North America, 1765. (L. B. C. 1016.) S. japonica (Japanese). A form of S. serrulata virgata. S. officinalis (officinal). fl., corolla often six or seven-parted; racemes shorter than the leaves, three to five-flowered. July. l. oval-obovate, 1 1/2in. to 2in. long, often rounded at apex, sub-acute at base, hoary-tomentose beneath. h. 10ft. Levant (naturalised in South-western Europe), 1597. (A. B. R. 631; Fl. Ment. 60; L. B. C. 928.) S. pulverulenta (powdery). fl. 1/2in. long, one to three together in the axils and at the tips of the branches, fragrant. Spring. l. oval or obovate, about 1in. long, sparingly puberulous above, scurfy-tomentose beneath. h. 1ft. to 4ft. South United States, 1794.

S. serrulata (slightly serrated).* fl., corolla five or six-lobed, pubescent; racemes terminating the lateral branches, shorter than the leaves. Spring. l. oblong, acuminate, 2 1/2in. long, acute at base, serrulated, glabrescent. Branches, petioles, racemes, and calyces fulvous-tomentose. India to Japan. A shrub or tree, sometimes 40ft. high. (B. M. 5950.) S. s. virgata (twiggy). l. tapering, acuminate, usually widest below the middle. S. japonica (R. G. 583; S. Z. F. J. 23) only differs from this variety in having somewhat pinkish-tinted buds, with a glabrescent calyx. SUBSOIL. The layer of soil existing at such a depth below the surface that it is not reached in the usual operations of gardening and agriculture, i.e., from about 1ft. below the surface downwards. In some localities, the Subsoil is of almost the same composition as the soil; but there is usually a considerable difference between them. Nor is it difficult to understand why this should be the case, in so far, at least, as regards the proportion of organic matter, and of the soluble foods of plants, in each; for plants draw a large share of their nourishment from the surface soil, and thus impoverish it of the substances used by them. On the other hand, such plants as die and decay on any piece of ground increase the proportion of organic matter in the surface soil, but add little, if any, to the Subsoil. The physical texture of the surface soil is also rendered more open by the numerous roots that traverse it; and this greater looseness is much increased by the operations of cultivation. The freer access of air and rain thus afforded permits a more rapid decomposition of the soil. The looser texture also permits rain-water to trickle down till it reaches the Subsoil, carrying with it soluble compounds out of the surface soil. If the Subsoil is clay, it retains what is carried down in this way, whether such additions are useful as food for plants, or poisonous to them. Hence, the Subsoil may become rich, so as to yield excellent crops when exposed to air and light; or it may be almost barren until the poisonous substances in it (e.g., Oxides of Iron) have been changed, by the action of natural agents, such as air and rain, or by the operations of agriculture, into harmless compounds.

The nature of the Subsoil exercises a very important influence on the fertility of the surface soil. If it is open and sandy, it allows the rain-water to drain away rapidly; hence, there is no reserve, in times of drought, to supply the place of that evaporated from the surface of the soil, and from the plants thereon, which suffer in their growth, or perish for lack of water. If, on the other hand, the Subsoil is clay impervious to water, the rain is caught, and collects in hollows, where it stagnates, with the usual ill-consequences of the surface soil becoming saturated and cold, and being rendered sour by the formation in it of organic acids, from the action of the water on decaying plant-remains. Clay Subsoils must, therefore, be broken up by the Subsoil plough, or by the spade and fork; but they should be well drained about one or two years before they are broken up, as wet clay coheres very quickly if merely cut through. Excellent results often follow the bringing of the Subsoil to the surface, by means of Subsoil ploughs or spades; and it is evident, from what is said above, that it must be an advantage to bring within reach of the roots of plants new soil, richly supplied with substances required by them, and that have been used up, to some extent, in the surface soil. Moreover, the new soil, when exposed to the atmosphere and frost, breaks up, and affords new food supplies, in addition to those washed into it by rain from the higher layers.

Where the Subsoil contains poisonous substances, it should not be disturbed, unless it is possible to let the ground lie fallow for a year or more. In this time, the danger will probably be removed by the action of the atmosphere upon the hurtful substances. To ascertain whether the Subsoil is hurtful, the following method has been employed: A flower-pot is filled with the Subsoil to be tried, and another is filled with ordinary soil, for comparison of results. Seed of the same kind is sown in both, and, if the Subsoil gives a good crop, this shows it to be safe, and worth bringing to the surface; but, if the crop is sickly and weak in the Subsoil, while good in the other pot, the Subsoil is evidently un-wholesome in its natural state, though it may be rendered fertile by exposure, for a time, on the surface.

SUB-TROPICAL GARDEN. A term applied to a portion of a flower garden or pleasure-ground devoted, during summer, to stately-habited foliage plants, which are arranged with a view to represent tropical vegetation. Many of the plants used are natives of tropical countries, and are, consequently, only available for placing outside during the hottest part of the year; but there are others of stately aspect which are quite hardy, and are invaluable for associating with them. Tropical plants of slow growth, which have to be kept under glass all the winter, require a great deal more space than can generally be afforded them; and as they are also very expensive subjects to procure in the first place, comparatively few gardeners have any at their command. One of the most important provisions for sub-tropical plants is shelter; their leaves in most instances are soon torn, and the plants disfigured, if exposed to rough winds. Shade and moisture are also necessary for many Tree and other Ferns and Cycads. There are numerous sub-tropical plants which may readily be raised from seed each spring, as they are quick-growing, and form quite large specimens before autumn, when planted out about the middle of June, in rich soil. Of these Albizzia lophantha, Castor-oil plants (Ricinus) in variety, Nicotianas, Solanums, Wigandias, and varieties of Zea are specially valuable. Cannas, too, may readily be raised from seeds in spring; but the plants are nearly hardy, and may afterwards be increased by division of the rootstock in spring. Of tropical plants the most serviceable are: amongst Palms--Chamaerops humilis, Livistona australis, L. chinensis, Phoenix dactylifera, Ptychosperma Cunninghamiana (often known in gardens as Seaforthia elegans), Trachycarpus excelsus and T. Fortunei. Musas--M. Ensete and M. superba. Tree Ferns--Alsophila australis and A. excelsa, Cyathea dealbata, Dicksonia antarctica. Cycas circinalis and C. revoluta may be plunged in sheltered positions along with the plants above-mentioned. Amongst other subjects also available are Arundinarias, Bambusas, Centaureas, Cordylines, Erythrinas, Fatsias, three or four species of Ficus, Funkias, the New Zealand Flax (Phormium tenax), Pampas Grass, &c. Other remarks on this subject will be found under Garden, and the descriptions and culture of plants referred to are given under their respective headings.