THE

QUARTERLY

JOURNAL OF AGRICULTURE.

STUDIES IN AGRICULTURE.-NO. II.

Rotation of Crops illustrated by the Failure of the Potato and the Red Clover.

THE two chief divisions of cultivated plants-Annuals and Perennials are naturally propagated, with few exceptions, in two principal ways, namely, by shedding their seeds or by producing young plants, in the various forms, according to the genera, of suckers, offsets, or runners above ground; or of new root-stocks (Rhizomata), bulbs, corms, or tubers, beneath the surface of the soil-all, so far as our limited knowledge can per ceive, regulated by that wise law of Providential wisdom, established to prevent any particular spot from being overoccupied with organized beings, that is, with more than can find wholesome food.

If we observe the proceedings of animals, we shall find this remarkable law in universal operation. When a kitten is old enough to lap milk from a basin, or to eat a bit of meat, the mother-cat, that had previously nursed it with so much care,fiercely defending it, at the danger of her own life, against the intrusions of strange dogs of thrice her size,-now relaxes in her maternal duties, and when it offers to suck or even to play, she hisses, growls, and spits at it, and often does not hesitate to cuff and buffet it about with her paws. Day by day, she becomes more spiteful to the former object of her tenderest care, till, at length, if it be not otherwise removed, she will with difficulty allow it to remain under the same roof with herself.

VOL. VIII.-NO. XL.

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The apparently barbarous instinct in the mother-cat, is naturally prompted, in the first instance, by the supply of milk in the udder becoming scanty, and no doubt causing uneasiness or pain when the kitten attempts to suck; but the final cause appears to be the diffusion of the species over a greater extent of surface, and more particularly the regulation of numbers to the supply of food.

Accordingly, we find that animals of prey are, with few exceptions, in small numbers in any given locality, such as the hereditary pair of magpies established for years about the trees of a Scotch farm-yard, and as regularly driving off their young to shift for themselves as the mother-cat does her kittens,-reserving for their own eating the hedge-laid duck's egg, or the captured chick, as well as the offal and garbage, of which the supply is too precarious to maintain a colony of magpies, as numerous as that of the pertinacious sparrows, their neighbours in the yard. A pair of corbies or ravens will, in the same way, maintain their hereditary territory intact from all intruders, because the sickly lambs which they can attack on a sheep-farm or two, or the braxy hoggs, must, in the most unhealthy seasons, be limited in number; and like the fabled Upas tree of Java, which will allow, it is said, no other plant to grow within its sphere, the ravens require exclusively all the food which the locality produces.

The sheep, on the other hand, on whose carcass the ravens prey, live harmoniously in large flocks, on the same principle of being able to find food, as the gregarious herbage (if I may use the expression) on which they feed, finds nourishment. Between the flocking sparrows or the gregarious sheep, and the solitary pair of magpies or ravens, there are numerous intermediate gradations, just as there are in the vegetable world, where we see bent and heath occupying miles of country almost exclusively, while the yew-tree and the ash will scarcely allow a blade of grass or any sort of weed to grow in their vicinity, lest they be robbed of the food which they absolutely require, and cannot travel in search of.

This highly interesting principle of diffusion among organized beings, is so well illustrated by the proceedings of the several species of ants, that I cannot put the subject in a more

striking point of view than by detailing what has passed under my own eye in numerous instances. It may be necessary to state, that there are three sorts of ants in every ant-hill, namely, females of a large size, males of a small size, and workers of a middling size, who forage for provisions, and construct the general habitation. At the pairing season, the males and the females acquire wings and escape from the colony, to the great consternation of the workers, as the colony depends on them for the increase of its population, and they consequently endeavour to prevent their egress.

Some of the females, after pairing, are usually captured by the working ants, and conducted back to the parent community to lay their eggs; and others are laid hold of by straggling parties of from two to a dozen workers, who do not return to the parent community, but commence small colonies on their own account. This explains the common occurrence of a great number of small colonies being formed in the immediate vicinity of each other, while sometimes the parent community is thereby quite broken up and the hill deserted. This happens frequently in the case of the red ant (Formica rubra) and the ash-grey ant (Formica fusca), both very common species in fields and gardens. In the case of the yellow ant (F. flava), again, and of the wood ant (F. rufa), this rarely occurs, the parent community often remaining on the same spot for years together.

When a female, after pairing, does not chance to fall in with any scouting parties of workers, she proceeds without their assistance to found a colony herself, in the same manner as is always done by the females of the social wasps and humble bees every spring. I have repeatedly verified this fact, both by confining a single female after pairing and witnessing her proceedings, and by discovering in the fields single females occupied in laying the foundations of a future city for their progeny.

Now it must be obvious to every observer, that this diffusion of the colonies of the red and the grey ants proceeds on the same principle, and is very similar to the diffusion of the winged seeds of the dandelion, groundsel, and thistle, or the projected seeds of the heart's-ease and touch-me-not (Impatiens Noli-metangere); while the stationary colonies of the yellow and the wood ant as much resemble the stationary trees and bushes in

their vicinity. The seeds fly to a distance from the mother plants in the same way as the female ants fly from the ant-hills where they had been hatched and reared, and the analogy holds no less in another remarkable circumstance:-within a few hours after the female ant has been impregnated, and as soon as she sets about her duties as a mother, she loses her wings (Huber says she strips them off herself), intended, it would appear, only as a temporary means of aiding her in going to a distance, in the same way as the fine feathery wings of the dandelion and thistle, after wafting the seeds through the air to a fresh spot of ground, fall off as of no farther use, and leave them to germi

nate.

It is very clear, without going the whole length of the well known doctrine of Malthus, that the due growth and thriving of both animals and plants must depend on a proper supply of food; for if the food be scanty in quantity, atrophy in one form or other must inevitably ensue. Other circumstances, however, require to be taken into account, besides the quantity of food, in all inquiries respecting the healthy growth of organized beings; and, in particular, it is indispensable not only that the food be wholesome, but that it may be adapted to peculiarities of individual constitution. One or two examples will serve to illustrate these interesting points.

Lord Kames planted a root of bryony in a rich garden border, without, perhaps, any view to experiment; but he soon found that the rich soil was not suitable, for the plant made all haste to get away from it, and established itself in the adjacent gravel-walk. In the same way, a plant of well-ink or brooklime (Veronica Beccabunga) in a syke, a drain, or a ditch, will extend its roots along the water-course, but will never send a single runner towards the contiguous dry ground of the bank, no more than the yellow stone-crop (Sedum acre), if growing on the dry bank, will extend a single shoot into the watery domain of the brooklime. We might as well expect to see the barn-door hen taking the water after the ducklings which she has hatched, or stealing away to lay her eggs in secret among the sedges, at the side of a pond; or to see the ducks at night mounting the steps to the hen-roost.

By a comparison of the numerous facts connected with the

diffusion of plants, I have been led to the inference, that plants, in general, will be found to deteriorate the soil, in proportion to their natural facilities of establishing a new progeny, at a distance from the deteriorated soil; and, consequently, that such facilities, or the want of them, furnish good indications to the cultivator, of the extent or rapidity of the deterioration caused by particular species. The nature of this deterioration, whether it arises from exhaustion or contamination of the soil, or both, is a subject of the highest interest, which will be considered as we proceed to illustrate the deterioration and the dif fusion.

Diffusion of Perennial Plants.

Leaving diffusion by means of seeds out of consideration for the present, perennial plants diffuse themselves, as has already been mentioned, by means of suckers, offsets, or runners above ground, and of new root-stocks, bulbs, corms, or tubers, beneath the surface of the earth. Each of these it will be convenient to illustrate separately.

Suckers. When a tree finds the soil deteriorated either by exhaustion or contamination, or both, so that the root-fibres can no longer supply the demand of the leaves and young shoots for sap, it endeavours to escape from the place where it grows, not by self-removal, which is impossible, but by sending up from the roots suckers, that may push their individual roots beyond the sphere of the deteriorated soil.

It will accordingly be found, that no healthy young tree, whether it be a fruit or a forest-tree, will push suckers so long as the soil it is planted in remains fresh, rich, and uncontaminated. But look at an old plum or pear tree in the orchard, or a decaying currant or gooseberry bush, or a rose-tree that has stood in the border for several years, and the suckers around them will shew how ill they relish the old deteriorated soil in which they grow, and how many efforts they make to travel out of it.

Nothing can more forcibly prove the great importance of annually digging in as much rich compost or fresh soil as possible, around the roots of all trees and bushes. Were it possible, indeed, to renew the soil entirely every two or three years,