difficulties arising from the mechanical condition of the soil, but a most important lesson will have been learnt, if this mechanical condition be looked upon as contributing a very important influence towards the general result. It is a fatal error to look upon the chemical composition of the soil as of itself indicating the productive powers of land. Such knowledge is of a very great value if it be rightly used, but it only represents one portion of the evidence by which the farmer should be guided in his decisions.

In the preparation of land for seed, regard must be had to the size of the seed, and the depths. beyond which they cease to germinate with safety. As a rule, the smaller the seed the less open the surface should be. If a case of shot were emptied on a pile of cannon balls it is clear that the shot would run from ball to ball, and pass down to a considerable depth. When proper care is not taken to have the land in suitable condition, the same thing happens in sowing the smaller farm seeds. Hence it will be found that many local practices hereby receive their explanation and complete justification.

Two very opposite practices are observed in reference to the seed-bed for swedes or turnips, which demand a notice in passing. On some lands we find the tillage completed two or three weeks before the seed is sown, the lapse of time being desired so that the moisture may rise up from beneath. It is a system which is especially designed for preserving moisture in the seed-bed, so that when the seed is

sown there shall be an immediate germination. In the other cases we have exactly the opposite policy adopted. Here the land is encouraged to become thoroughly dry, and, so far from any attempt to prevent its exposure to the sun and air, every opportunity is sought for the tillage operations to assist in making the land not only fine, but dry. The seed, when sown in such a dry seed-bed, remains without any commencement of germination until heavy rain has fallen, and then the growth is so rapid that it rushes into rough leaf with great speed. The danger in the former case is that growth having been commenced by means of the moisture so carefully preserved in the soil, if rain should be long delayed the plant may perish before the needed supply of water is received. The peculiar character of the weather during recent years has been so exceptional that these cases have rarely arisen, but when we have a return of dry seasons the same difficulties will be revived.

We have in the French clover (Trifolium incarnatum) very exceptional mechanical conditions required. In this case the free and open condition of the soil is a distinct disadvantage, and the most successful cultivation has been that which secured a hard and firm seed-bed-rolling the land after the seed has been sown being preferable even to a light harrowing.

A farmer is not always ready to justify his practice and give his reasons for doing what he knows to be most desirable for the soil of his farm, but the

intelligent student will endeavour to seek out the germ of truth embodied in the successful practice of the farmer, and, whilst learning a lesson in reference to the management of the land, he will endeavour to determine the cause of success.

CHAPTER XVII.

PLANTS can only make growth when they have a proper supply of the materials they need for building up their various parts. They have no means for maintaining growth, except by making use of the food they receive. We very generally recognise the fact that animals require proper food for promoting their health and increasing their growth, but we do not as generally remember that plants have an equal necessity for suitable food. We supply animals with their food in many cases, and in other instances we see the supplies on which they subsist. The circumstances are not favourable for seeing plants taking in their food. They are fixed in the soil, and their search for food is carried on under circumstances and conditions which are to a very great extent beyond our observation. If we could see the changes going on in the soil we should be very little wiser, for we should only observe minute supplies of water passing into the roots of the plant. If we could watch the leaves perfectly, we might find these breathing in and throwing off gaseous matter, in a

manner somewhat similar to animals, although that gaseous matter (or, familiarly speaking, air) would not be of the same composition in the two cases. The food of plants, however, is received by them under circumstances which are greatly beyond our ordinary observation. Scientific research has unveiled these hidden and invisible proceedings, consequently we have a tolerably complete knowledge of the manner in which plants receive their food, and what materials they use for building up their several parts.

A person may have a very ingenious apparatus placed in his hands, so carefully enclosed by an external covering that he is quite at a loss to form any opinion as to the internal arrangements or the materials of which it is constructed. When the apparatus is taken to pieces and examined, he may then discover what materials were employed in its construction. By means of chemical analysis this has been done with all our cultivated plants, and thus we know what are the materials of which they are built up. We find that a great variety of substances have been so used, and we also observe a certain regularity in the substances which are selected for the work to be done. In determining the composition of plants chemists have found it convenient to separate these materials into two distinct groups. The one group consists of those bodies -organic matters-which pass off in vapour and smoke when the plant is burnt, and the other group consists of those bodies which remain as the ash.

Thus we have what are known as the ashes of plants," and these represent the mineral matter which such plants contained. This mineral matter may be regarded as having given strength and rigidity to the plant during life, enabling its soft and fleshy organs the better to discharge their functions. Thus the structure of the plant consisted of two classes of bodies the soft matter forming the various organs of the body, and hence known as organic matter, and the mineral substances which gave them strength, which are sometimes also spoken of as inorganic matter, or the ash of the plant. Both are as essential for a healthy plant, as the skeleton and its fleshy coverings are necessary for the body of an animal.

The various materials which are found in the perfect plant have necessarily been supplied to that plant in its food; hence we get a very distinct guidance in determining what is necessary as food, if we take note of the materials which have been made use of for the construction of the fully grown plant. The question very naturally arises as to the substances which are so employed, because the plant must have received all of them by means of its food. Those substances which are found in the ash-or the inorganic matters of plants, may first receive a