219. Plants take the greater part of their food, which must be either in a gaseous or liquid state, partly through the spongioles of their roots, and partly through the pores in their leaves; and consequently, it is of the greatest importance not only to keep these organs, which are of the most delicate con-structions in a condition to exercise their functions properly; but to take care, that they come in contact with the food required by them. The food of plants consists of carbon, (which is found partly in the ground, and partly in the air,) oxygen, hydrogen, and nitrogen, which are absorbed by plants partly from the air, and partly from the water with which they are supplied; and numerous mineral or earthy substances, which are produced from the ground, but which must be dissolved in water, or reduced to the state of gas, before they can be absorbed by the plant. Although it is clear that the principal organs through which plants take their food are the roots and the leaves, there is no doubt that some portion of it is absorbed by the green part of the stem and branches. The leaves are also useful in assimilating or digesting food; and they act as organs of respiration and perspiration, by throwing off superfluous air and water.

It is quite evident that these various functions cannot be performed properly if the surface of the leaf is loaded with soot, or dust, or any other substance which chokes up the pores; and consequently syringing the leaves is one of the most important points of culture in a suburban garden. The roots only take up food through what are called their spongioles, from their resemblance to little sponges. These spongioles consist entirely of cellular tissue and mucus; and, as they are unprotected by any epidermis or skin, they are easily rotted if exposed to too much moisture; and, on the other hand, if they are kept too dry they lose their power of expanding and contracting to receive moisture, and to send it up through the other vessels of the plant.

220. Manures should be used with caution in suburban gardens, as the plants are seldom in a state to digest properly those which are of a very strong nature. Animal manure to plants is like animal food to human beings, and requires a healthy frame to assimilate it. Vegetable mould, formed of rotten leaves mixed with sand; and carbonate of ammonia, mixed with water, will be found the best manures for delicate plants growing in a confined situation.

221. - The soil in suburban gardens is very often in a very bad state for growing plants. This is most generally the effect of want of drainage; and as most suburban gardens are over watered, the water which cannot escape chills the soil, and, in some cases, rots the roots of the plants. It is true that the latter evil is only seldom felt; but the coldness of the soil is a fact of every day occurrence, though comparatively few persons are aware of its existence. "Drained land," says Dr. Lindley, "is. in summer 10° or 20o warmer than water-logged land." The reason "consistsin the well-known fact that heat cannot be transmitted downwards through water." Thus, neither the heat of the sun nor the warm rain can penetrate to the roots of plants in ill-drained land; even boiling water poured on the surface would have no effect in warming soil on which cold stagnant water naturally stands. Air also cannot reach the roots of plants grown in soil of this nature; .and, as Dr. Lindley observes, it is as important to permit the access of air to the roots as to the leaves: "both extremities of plants feed on air, the roots more than the leaves.

Place a plant in a place where air can gain no access to its leaves and they fall off, to be followed by the decay of the stem: roots, under the same circumstances, will gradually shrink and die." - (Gard. Chron., 1849, p. 35.)

222. The principal conditions, therefore, necessary to the health of plants in suburban gardens are, to keep the soil open and friable, so as to admit freely of the passage of minute particles of air and water to the roots of plants; to syringe the leaves of the plants as frequently as possible, so as to keep them clear from all imparities; and not to overwater the roots. Where rose trees are grown, it is a great point to keep them clear of aphides; and the best mode of doing this is to make a little brush of pieces of bast mat, tied together, sod fixed on a bit of stick. This brush is much softer, and less likely to injure the delicate texture of the young shoots, than a brush made of hair or bristles.

223. It is necessary that the food of plants should be in a state of minute subdivision when it is presented to the spongioles of the roots; and it is also necessary that these delicate organs should not be plentifully supplied with food, unless the leaves are kept in a healthy state, so as to digest it properly. Thus, if the roots are supplied with abundance of water, manure, and air, and no water is given to the leaves, which are suffered to remain laden with soot or dust, the spongioles, acting mechanically, will take up more food than the plant can digest; and its vessels becoming choked up, "the usual circulation of the fluids will be impeded, and it is not surprising that the plant should droop, that its flowers should not expand, or that its fruit should shrivel or drop off prematurely, and that in the end it should die; as in fact it may be said to expire of apoplexy, brought on by indigestion."- - ( Gardening fir Ladies, 1st edit, p. 27.)

224. The want of light is another disadvantage which attends suburban gardens. Light is essential to plants to produce the chemical changes which ought to take place in their leaves; and suburban gardens, from their small size, and the height of the surrounding houses, have frequently their largest portion in the shade during the greater part of the day. Light is particularly necessary to the production of flowers, and to the ripening of fruit; and hence suburban gardeners find it very difficult to grow showy flowers, and to ripen fine fruits.