Incredible as it may sound, the calla is not a flower, and the snowy "spathe" which enfolds its golden head is neither a petal nor a sisterhood of petals. It is a foliage-leaf, become big and beautiful in order to lure the marsh-flies of the calla's native haunts to visit and fertilize its flowers; for the real flowers are not one, but legion. They have lost everything which ever belonged to them except a few stamens, or a few stamens and a pistil, as the case may be. They completely cover the column or spadix, which stands up inside the enfolding leaf, and in the calla of commerce they are so massed together that it is difficult to distinguish them even with a lens.
Fig. 32. - Sweet-flag (Acorus Calamus).
The calla's past condition may be surmised from the present state of some of its humble cousins which are to be found around ponds and in bogs in the northern and central United States.
In the sweet-flag or calamus, for instance, the flowers which crowd the spadix are perfect and complete (Fig. 32).
Each has six flower-leaves, which are now reduced to half-transparent greenish scales, six stamens, and a three-celled ovary enclosing several seeds (Fig. 33).
By studying these flowers we see how a mass of perfect little lilies may have been altered into a mere club of stamens and pistils.
As the lilies are squeezed together their flower-leaves have no chance to reach a perfect development. So the spathe, at first a mere leafy sheath, begins to assume the duties which they have abandoned, and, by making a show in the world, helps to lure flying-insects to the blossom-colony. The downward path is as easy in nature as it is in morals. Generation after generation the partially-superseded flower-leaves pale and dwindle, till, as in the calla, they are wholly superseded, and the spathe completely usurps their office of insect-luring.
The cat-tail flag is like a calla, with its stami-nate and pistillate flowers separated, and with its creamy leaf torn away. It depends upon the wind for its pollen-carrying, and hence has no need of an insect-lure. Its flowers are reduced to the lowest possible terms, and may represent the last step in degeneration.
In early summer the cat-tail is a two-story arrangement (Fig. 34). The upper part is of golden-green and soft-like chenille, while the lower portion is darker in hue and more solid to the touch. The golden-green upper-story is a mass of stamens, or, to speak strictly, of reduced staminate flowers, inserted directly on the central stalk and mingled with long hairs. By latter July the stamens have shed their pollen and shrivelled, and they and their accompanying hairs have dropped off, leaving a bare stalk behind them. The darker and more substantial lower-story is a mass of blossoms, each reduced to a little stalk bearing one pistil and a few bristles. When the ovaries have ripened into minute fruits - not seeds, though we should incline to call them so - the bristles will buoy them up on the autumn winds and enable them to fly far in search of new homes (Fig. 35). To the evolutionary botanist the little stalk which supports the cat-tail ovary suggests the stalk of a perhaps once perfect flower, and the bristles the flower-leaves that used to be.
Fig. 33. - A single floret of the sweet-flag.
Fig. 34. - June aspect of the cat-tail flags.
Fig. 35. - Single florets of the cat-tail flag.
a, Young staminate (or male) floret; b, older staminate (or male) floret; c, pistillate (or female) floret.
So starting from the complete and perfect lily with six creamy flower-leaves, six stamens, a three-celled ovary, and a seed-vessel splitting into three, we can trace every step in a downward course till we come to the lowly estate of her distant poor relations, the cat-tail flags.
But in members of the lily's kin, of high or low degree, the fibro-vascular bundles of the stem are "closed," the leaves have parallel veins, the parts of the flower follow more or less closely the rule of three, the ripe seed contains abundant nourishment, packed around the germ, and the sprouting plant has one cotyledon.
And in the kindred of the rose, aristocratic or plebeian, the fibro-vascular bundles of the stem are "open," and the leaf-veins branch into complicated networks. The parts of the blossom are in fours or fives. The nourishment garnered for the germ is generally packed into the cotyledons, and those cotyledons are two and opposite.
So from the very first the great law of heredity asserts itself, and the type of the race is impressed upon the germ while it yet lies dormant in the seed.