Page:Popular Science Monthly Volume 28.djvu/89

Rh that all these questions arc yet by any means finally solved. The sole object of the present paper is to point out the common principle running through the variations of the clover pattern, and to suggest such partial explanations of their causes as have yet occurred to a single observer.

Suffocated clover is another of the tiny creeping types, apparently protected for the most part against browsing quadrupeds. It is a wee tufted form, with minute flowers stuck close in small dense heads, as if gummed to the short stems, and very crowded along their course. We may regard it as the last effort of a very degraded race to keep up its existence in the most closely gnawed pastures, on sand or gravel, where only very dwarfed and scrubby plants can escape destruction. The reader will notice that under such circumstances two types of clover succeed, each in its own way. If the heads become very small, close, and inconspicuous, or tightly pressed against the wiry trailing stems, they escape the observation of browsing animals. If, on the other hand, though tall and noticeable, they develop prickly or stiffened teeth, they are rejected as unfit for food by the creatures which devour the surrounding herbage.

Reversed clover takes its name from a peculiarity which seems to, be connected with its mode of fertilization, for it has its standard petal turned outward, instead of inward as in all other clovers. The meaning and object of this change I do not know; but its most marked feature is still one bearing upon preservation of the seed, for, after flowering, the upper part of the calyx becomes much inflated, and is traversed by large membranous veins. At the same time it arches over the lower half, leaving three small teeth below, and two swollen ones at the top, so as to form a sort of bladder-like capsule over the concealed pod. In this case, again, the protection is obviously designed against birds or insects. In the curious strawberry clover, common among dry meadows and road-sides in Southern Britain, the same device has been carried a step further. Each flower in the head is here surrounded by a long involucre of lobed bracts, and, after flowering, the calyx swells immensely, so as to transform the entire head into a compact globular ball of little bladders, each inclosing a single pod. This arrangement has been popularly compared to a strawberry, but it is much more like a raspberry, being a delicate pink in hue, and composed of twenty or thirty small round capsules. The upper half of the bladder is likewise thickly covered with fine down, doubtless very objectionable to the skin of the tongue, and the whole is netted and veined in the most delicate and beautiful fashion. Hardly any other clover possesses so advanced a plan for protecting its little pod.

Another type is presented to us by the large crimson clover, not truly indigenous in Britain, but commonly cultivated for fodder in the south of England. It is a soft, hairy plant, and, like other fodder clovers, it does not possess any very advanced protective device. Still,