Page:Popular Science Monthly Volume 42.djvu/91

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Protective organs or substances are frequently increased in the vicinity of flowers. Long ago Erasmus Darwin wrote: "The flowers or petals of plants are perhaps, in general, more acrid than their leaves; hence they are much seldomer eaten by insects." "Many caterpillars will rather die than eat the flowers of the plant whose leaves are their special food."[1] But insects are not the only foes who steer clear of petals. Kerner gives a long list of plants whose leaves are eaten by herbivora, the flowers untouched. In our own land the blossoms of the waysides and fields—May-weed, buttercups, daisies, dandelions, sorrel, wild carrot, etc.—by their very abundance witness to their immunity from the attacks of grazing animals.[2] The survival of many showy flowers in St. Helena, notwithstanding the introduction of goats, which have destroyed the luxuriant forests, may perhaps be due to the beauty which brands them unpalatable.

The conspicuousness of all of these species is the noteworthy point. They are landmarks, doubtless, to the lower animals as to us. That blossoms are most completely shunned when they are large and showy is almost axiomatic. If bright flowers tasted well, they would be speedily annihilated. The majority of good fodder plants have insignificant flowers.[1]

There is still another class of enemies which may be prevented from attacking flowers by the disagreeable chemical properties of their conspicuous petals. These are the birds. Mr. Brockhurst writes that in the dry summer of 1880 the sparrows, seeking pollen, destroyed his crocuses, preferring the yellows to the purples and whites. They also attacked the primroses, devouring hundreds of them in one morning. Orioles have been seen to bite through the corollas of the trumpet-creeper and golden currant. Young seeds and soft petal tissues would certainly seem to be dainty bird-fare, and would surely be more often so used were they not chemically protected from such injury. As things are, however, other food seems to be preferred when it can be found. In addition to the need of defense against rain, and of adaptation to the form and size of the chosen visitors, necessity of keeping the pollen, nectar, and ovules from destruction by birds may have helped in the formation of tubular and palated corollas. Flowers need the beauty of Helen to attract lovers, the guile of Penelope to discriminate between the true and the false; to provide for the one, and against the others.

IV. Mimicry.—Mr. Bates found in South America and Mr. Wallace in the Malay Archipelago several genera of very abundant, brilliant butterflies which birds refused to eat; and, accom-

  1. 1.0 1.1 Kerner.
  2. The disagreeable substances are volatile, disappearing when the flowers are dried