On the Varieties of the Mulberry Tree as Food for the Silkworm (Part I).
1. “On the Varieties of the Mulberry Tree as Food for the Silkworm,” (Part I.), by T. C. Batchelor.
It is a conceded point, that the food which agrees best with the Silkworm is the leaf either of the red or of the white mulberry tree. The quality, however, of the silk does not altogether depend on the food, but also on the degree of temperature in which the Silkworm has been reared. As there are mulberry trees of different qualities it might be imagined that these differences influence the state of the Silkworm. There are five different substances in the mulberry leaf: 1st, the solid or fibrous substance; 2nd, the colouring matter; 3rd, water; 4th, the saccharine matter; 5th, the resinous. The fibrous substance, the colouring matter, and the water, excepting that which in part composes the body of the Silkworm, cannot be said to be nutritive to it. The saccharine matter is that which nourishes the insect, that enlarges it, and forms its animal substance. The resinous is that which, separating itself gradually from the leaf, and attracted by the animal organisation, accumulates, clears itself, and insensibly fills the two reservoirs, or silk-vessels, which form the productive economy of the Silkworm. According to the different proportions of the elements which compose the leaf, it follows that cases may occur in which a greater weight of leaf may afford less that is useful to the Silkworm, either for its nourishment, or with respect to the quantity of silk it may yield. Thus the leaf of the black mulberry, though hard and tough, which is given to silkworms in some of the warm climates of Europe, produces abundant silk, the thread of which is strong, but coarse. The leaves of the
red and white mulberry trees, planted in high lands and in light soils, and exposed to cold dry winds, produce large quantities of strong silk, of the purest and finest qualities. The leaves of the same kinds of trees, planted in damp situations, in low grounds, and in stiff soils, produce less silk, and of a quality less pure and fine.
The less nutritive substance the leaf contains, the more leaves must the Silkworm consume to complete its development. The result must therefore be, that the Silkworm which consumes a large quantity of leaves that are not nutritive must be more fatigued and more liable to disease than the Silkworm that eats a smaller proportion of more nutritive leaves. Notwithstanding all this, experience proves that, all things balanced, the quality of the soil produces but a very slight difference on the quality of the leaf; that which will appear most evident is, that the principal influential cause of the fineness of the silk is the degree of temperature in which the Silkworm is reared. There is another fact to be observed, that an old mulberry tree will always produce better leaves than the young tree, and as the tree grows older, of whatever quality it may be, the leaf diminishes in size, and improves so materially that it attains a very excellent quality.
Mr. Brady, the well-known sericulturist of New South Wales, writes to me that the Morus multicaulis is on the whole by far the best tree for its earliness, ready growth, and quantity of leaves. Count Dandolo gives a description of a tree called the Tuscan mulberry, which closely resembles the Morus multicaulis, and says that if the leaves are allowed to get matured on the tree, and those only given in the last stages of feeding, the Silkworms answer every purpose required. I received lately from a silk merchant in England specimens and circulars, giving names and descriptions of trees that are used in Europe, viz., Morus japonica, a large-leaved tree, Lombardy rose, and Morus alpina, suitable for cold and exposed situations. Some plants of M. multicaulis that I planted on a steep hill-side two years since have produced a smaller but much thicker leaf. As the growth of mulberry trees and the rearing of silkworms are two different branches of industry, and are often followed apart, there is no reason why this should not be done here, and there are many reasons why it should be the more preferable. In the early stage of the industry it would leave to the cottager the simple task of rearing the trees, which would largely recompense him for his labour. A few statistics will not be out of place here, to show what returns may be expected from growing mulberry trees. Assuming that an acre of land is planted with 400 mulberry trees one year old, at the first but few leaves can be taken, but the second year each tree should produce one shilling's worth of leaves, or at the rate of £20 to the acre, and increasing in value every year.
But it would be a mistake to suppose that the mulberry tree can be raised
without cost or labour; at the present moment the cost of planting an acre of ground would be considerable, because the trees are scarce, and cannot be obtained in sufficient numbers; but the cost of trees will diminish yearly, as they can be grown readily from cuttings, so that commencing with a few trees the number can be increased at little cost. The cultivation of the tree requires attention, to grow luxuriantly and stand the waste it is made subject to by being stripped of its leaves. The mulberry tree must be well manured, but the cost of this would not equal that of cultivating crops of grain, while after the two first years the returns from ordinary farming would bear no proportion to those to be obtained from growing mulberry trees.
In a country like this, where land is cheap, and where, from the scantiness of labour so little is made of it, the sacrifice would be nominal were every small holder of land to plant only a few hundred trees on the sides of the hills; and on many spots where land is suffered to lie uncultivated the mulberry tree would thrive well.
In conclusion, I have to express my firm conviction that sericulture may be made one of the most valuable industries this colony can possess; and if I succeed in inducing small holders of land to cultivate mulberry trees, the object for which I have laboured will be attained.