In the application of moisture to the soil, the structure which is described in a previous chapter, will be found to present facilities, which peculiarly adapt it for the growth of these plants. In Persia, and the neighbouring countries, where the Melon is so successfully grown, the ground is irrigated by means of numerous channels, which, from the limitation of their exposed surface, are not peculiarly adapted to supply atmospheric moisture; but are yet sufficiently numerous to secure the perfect irrigation of the soil, within the reach of the roots. The tubes or shafts, represented at (_n_) in the sketch referred to above, are intended to communicate directly with a layer of coarse open material, extending entirely over the top of the tank, and beneath the soil; by means of these a supply of water should be poured beneath the soil, which will thus keep that portion immediately about the young roots, in a constant and complete state of saturation, by means of the steam which will arise, in consequence of the heat from the tank. A uniformly warm, and a thoroughly moist soil, will be thus easily secured, which are two important points in the growth of Persian Melons. It must be recollected that these conditions for supplying moisture, are recommended only during the time of growing the plants, and swelling the fruit; but as these latter approach their maturity, the degree of moisture must of course be gradually diminished.
In connection with this moistened and genial soil, the Melon has naturally the advantage also, of powerful sun heat, and intense light; and these are two conditions which it is indispensable should be supplied in artificial cultivation, as fully as they can possibly be obtained. It is by means of the moisture of the soil, that the plants are enabled to grow on rapidly and vigorously, because that moisture renders the food contained in the soil, soluble, and therefore available to the roots; but the elaboration and assimilation of this food depends on the degree of _light_ and _heat_ with which they are supplied: without these conditions, to convert the crude sap, by their united agency, into organic compounds, such as lignin, gum, starch, and sugar, and to induce their deposition, the fruit will indeed be formed--it will grow, and perhaps may even tempt the eye; but unless these chemical and vital changes have taken place in its constituent parts, the eye, as it frequently happens, will have been deceived; and instead of the palate being gratified by a mature and luscious fruit, it will find nothing but a tasteless mass of pulp. The plants, therefore, cannot, in our latitude, receive too intense a degree of solar heat, or of light.