PKINCIPLES.] HORTICULTURE 217 Reversion. In modified forms of plants there is fre quently a tendency to "sport" or revert to parental or ancestral characteristics. So markedly is this the case with hybrids that in a few generations all traces of a hybrid origin may disappear". The dissociation of the hybrid element in a plant must be obviated by careful selection. Germination. The length of the period during which seeds remain dormant after their formation is very variable. The conditions for germination are much the same as for growth in general. Access to light is not required, because the seed contains a sufficiency of stored-up food. The temperature necessary varies according to the nature and source of the seed. Some seeds require prolonged immersion in water to soften their shells ; others are of so delicate a texture that they would dry up and perish if not kept constantly in a moist atmosphere. Seeds buried too deeply receive a deficient supply of air. As a rule, seeds require to be sown more deeply in proportion to their size and the lightness of the soil. The time required for germination in the most favourable circumstances varies very greatly, even in the same species, arid in seeds taken from one pod. Thus the seeds of Primula japonica, though sown under precisely similar conditions, yet come up at very irregular intervals of time. Germination is often slower where there is a store of avail able food in the perisperm or albumen, or in the embryo itself, than where this is scanty or wanting. In the latfeer case the seedling has early to shift for itself, and to form roots and leaves for the supply of its needs. Selection. Supposing seedlings to have been developed, it is found that a large number of them present considerable variations, some being especially robust, others peculiar in size or form. Those most suitable for the purpose of the gardener are carefully selected for propagation, while others not so desirable are destroyed ; and thus after a few generations a fixed variety, race, or strain superior to the original form is obtained. Many garden plants have originated solely by selection ; and it is certain that, quite independently of cross-breeding, much could still be done to improve our breeds of vegetables, flowers, and fruit by more systematic selection. The re markable results obtained in the case of Major Hallett s pedigree wheat and Mr Bennett s hybrid tea-roses are in stances in point. Two robust-growing varieties of potato, the "Magnum Bonum" and the "Champion," have been found to resist better than others the attacks of fungus to which the plant is liable. Whatever may be the cause, whether the possession by the tuber of a more than ordi narily thick skin, or other peculiarity, it is obvious that selection with a view to the development of this quality might be productive of the most important results. Darwin recommends, as a means of improving health and fertility by intercrossing without loss of purity of race, to sow in alternate rows seeds grown under as different conditions as possible. Large and well-formed seeds are to be preferred for harvesting. The seeds should be kept in sacks or bags in a dry place, and if from plants which are rare, or liable to lose their vitality, they are advantageously packed for transmission to a distance in bottles or jars filled with earth or sphagnum moss, without the addition of moisture. Cuttings and entire plants may be transported in wide- mouthed bottles. It will have been gathered from what has been said that seeds cannot always be depended on to reproduce exactly the characteristics of the plant which yielded them ; for instance, seeds of the greengage plum or of the Ribston pippin will produce a plum or an apple, but not these parti cular varieties, to perpetuate which grafts or buds must be employed. (M. T. M.) PART II. THE PRACTICE er HORTICULTURE. The details of horticultural practice naturally range under the three heads of flowers, fruits, and vegetables. There are, however, certain general aspects of the subject which will be more conveniently noticed apart, since they apply alike to each department. We shall therefore first treat of these under four headings : formation and pre paration of the garden, garden structures and edifices, garden materials and appliances, and garden operations. I. Formation and Preparation of the Garden. 1. Site. The site chosen for the mansion will more or Sit*, less determine that of the garden, the pleasure grounds and flower garden being placed so as to surround or lie con tiguous to it, while the fruit and vegetable gardens, either together or separate, should be placed on one side or in the rear, according to fitness as regards the nature of the soil and subsoil, the slope of the surface, or the general features of the park scenery. In the case of villa gardens there is usually little choice : the land to be occupied is cut up into plots, usually rectangular, and of greater or less breadth, and in laying out these plots there is generally a smaller space left in the front of the villa residence and a larger one behind, the front plot being usually devoted to approaches, shrubbery, and plantations, flower beds being added if space permits, while the back or more private plot has a piece of lawn grass with flower beds next the house, and a space for vegetables and fruit trees at the far end, this latter being shut off from the lawn by an intervening screen of ever greens. Between these two classes of gardens there are many gradations, but our remarks will chiefly apply to those of larger extent. The almost universal practice is to have the fruit and vegetable gardens combined ; and the flower garden may sometimes be conveniently placed in juxtaposition with them. When the fruit and vegetable gardens are combined, the smaller and choicer fruit trees only should be admitted, such larger-growing hardy fruits as apples, pears, plums, cherries, <kc., being relegated to the orchard. Ground possessing a gentle inclination toward the south is desirable for a garden. On such a slope effectual drain ing is easily accomplished, and the greatest possible benefit is derived from the sun s rays. It is well also to have an open exposure towards the east and west, so that the garden may enjoy the full benefit of the morning and evening sun, especially the latter ; but shelter is desirable on the north and north-east, or in any direction in which the particular locality may happen to be exposed. 2. /Soil and Subsoil. A hazel-coloured loam, moderately Soil, light in texture, is well-adapted for most garden crops, whether of fruits or culinary vegetables, especially a good warm deep loam resting upon chalk ; and if such a soil occurs naturally in the selected site, but little will be re quired in the way of preparation. If the soil is not moderately good and of fair depth, the situation is not an eligible one for gardening purposes. Wherever the soil is not quite suitable, but is capable of being made so, it is best to remedy the defect at the outset ; and as it will be found easier to render a light soil sufficiently retentive than to make a tenacious clay sufficiently porous, a light soil is to be preferred to one which is excessively stiff and lieavy. It is advantageous to possess a variety of soils ; and if the garden be on a slope, it will often be practicable to render the upper part light and dry, while the lower emains of a heavier and damper nature. Natural soils consist of substances derived from the decomposition of various kinds of rocks, the bulk consisting of clay, silica, and lime, in variousproportions. As regards ^reparation, draining is of course of the utmost importance.
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