The shapes of the leaves themselves are also largely due to the same cause, every leaf being so designed in form and outline as to interfere as little as possible with the other leaves on the same stem, as regards supply both of light and of carbonaceous foodstuffs. It is only in rare cases, like that of the water-lily, that perfectly round leaves occur, because the conditions are seldom equal all round, and the incidence of light and the supply of carbon are seldom unlimited. But wherever leaves rise free and solitary into the air, without mutual interference, they are always circular, as may be well seen in the common nasturtium and the English pennywort. On the other hand, among dense hedgerows and thickets, where the silent, invisible struggle for life is fierce indeed, and where sunlight and carbonic acid are intercepted by a thousand competing mouths and arms, the prevailing types of leaf are extremely cut up and minutely subdivided into small lace-like fragments. The plant in such cases can't afford material to fill up the interstices between the veins and ribs which determine its underlying architectural structure. Often indeed species which grow under these hard conditions produce leaves which are, as it were, but skeleton representatives of their large and well filled-out compeers in the open meadows. It is only by bearing vividly in mind this ceaseless and noiseless struggle between plants for their gaseous food and the sunshine which enables them to digest it that we can ever fully understand the varying forms and habits of the vegetable kingdom. To most people, no doubt, it sounds like pure metaphor to talk of an internecine struggle between rooted beings which cannot budge one inch from their places, nor fight with horns, hoofs, or teeth, nor devour one another bodily, nor tread one another down with ruthless footsteps. But that is only because we habitually forget that competition is just as really a struggle for life as open warfare. The men who try against one another for a clerkship in the City, or a post in a gang of builder's workmen, are just as surely taking away bread and butter out of their fellows' mouths for their own advantage, as if they fought for it openly with fists or six-shooters. The white man who encloses the hunting grounds of the Indian, and plants them with corn, is just as surely dooming that Indian to death as if he scalped or tomahawked him. And so too with the unconscious warfare of plants. The daisy or the plantain that spreads its rosette of leaves flat against the ground is just as truly monopolizing a definite space of land as the noble owner of a Highland deer forest. No blade of grass can spring beneath the shadow of those tightly pressed little mats of foliage; no fragment of carbon, no ray of sunshine can ever penetrate below that close fence of living greenstuff.