Scarcely any vegetable growth is so plentiful as grass, which has been used in that sense by the highest of all authorities, “which to-day is, and to-morrow is cast into the oven.” Grass forces its way everywhere—not only in cultivated grounds, but in the wildest of lands, where there is scarcely any nurture for it. Even among the habitations of mankind the grass will have its way, and clothes deserted housetops with verdure, and forces itself between the stones that pave neglected streets.
Place side by side some of these stones, together with a very young and tender Grass-blade, and it will seem to be impossible that so fragile an object should be able to exert any influence on the solid stone. Let any one try to push a sharp skewer between the stones, and he will find that he has to exert power sufficient to crush a thousand grass-blades. Yet these slight and delicate objects will force themselves between the stones, and sometimes to such an extent as to cover the whole roadway with verdure.
The force which is employed is simply marvellous, and can only be appreciated by those who know the resisting power of earth, however dry and loose it may be. Even sand has so strong a resistance that tents can be pitched in the desert without difficulty. Of course the ordinary tent-peg would be useless, but the desert dwellers can pitch their tents with perfect security. They fasten the tent-rope to a branch or piece of bush, scrape a hole in the sand, put the bush into the hole, cover it up again, and it will withstand almost any strain, though it be only covered with a few inches of sand.
When miners blast rocks with gunpowder, they take advantage of the resisting power of sand. They bore a suitable hole, place a charge of gunpowder at the bottom, and then merely pour loose sand into the hole until it is filled. When the powder explodes, the rock or coal is shattered to pieces, but the sand is not blown out of the hole. This operation is called “tamping.”
Every one, again, knows how firm are gate-posts, and how they resist the weight, jarring, and leverage of a heavy gate, all because they are sunk a little way into the earth.
Considering, therefore, that such fragile things as young grass-blades can force their way through the superincumbent weight, we can but be amazed at the aggregate of active force which is in full operation in every pasture field and garden lawn.
As far as I know, not being much of a botanist, every seed that springs up does so on the wedge principle, though the form of the wedge may be varied.
A terrible example of the force which is exercised by this principle among the vegetables is shown in some parts of the world where the Aloe flourishes in a wild state. In our colder clime the Aloe, though it does live in the open air, is a slow-growing plant. But, in its own land, it shoots up with a surprising vigour, and its sharply pointed and saw-edged leaves are said to grow to the extent of six inches in a single night.
Taking advantage of this rapid, and, at the same time, powerful growth, the natives, when they want to punish a man with more than ordinary severity, tie him hand and foot, and bind him to the earth just over a sprouting aloe plant, and leave him there. In twenty-four hours the man is nearly certain to be dead, the aloe-leaf having forced itself completely through his body. Or, if he be not actually dead, he lives in frightful tortures, which are continually increased by the flinty point and notches forcing themselves slowly, but surely, through the body.