Page:Popular Science Monthly Volume 42.djvu/93

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are resorted to. Most insect-like orchids resemble brilliant butterflies, which, are as a rule unpalatable, and therefore enjoy comparative immunity from attack. May not the flowers be protected by the resemblance, as the defenseless butterflies discovered by Wallace are? Some such reason as this makes it more easy to comprehend the need of such elaborate development for which adaptation to small flies or bees, as in the case of lady-slippers, is hardly a satisfactory explanation. Nature is too economical to spend so lavishly for the accomplishment of what has been done much more simply in other ways. The desirability of combined attraction and repulsion brings with it the need of many new wiles. If "all things are fair in love and war," much may be expected of a man or flower engaged at the same time in both pursuits.

Another orchid (Pogonia ophioglossoides) is very difficult to find because of its great likeness to the much more abundant Indian cucumber which lives in the same places. In company with two botanists and a gardener well versed in the ways of the woods, I have spent hours in finding half a dozen specimens. Mr. Gibson, too, met with the same difficulty, actually treading the orchid under foot, "the imitative whorled foliage of the medeolas having beguiled my discrimination." Surely, though, it is the pogonia which is the imitator. It is the rare form, fulfilling all the conditions of mimicry. The two plants dwell together. The rare one differs from its allies; there is no other pogonia, and, indeed, no other orchid of our flora which has its leaves whorled on the stem. The whole appearance of the plant is decidedly non-orchidean, and, so far as pressed specimens show, the flower continues the imitation, for the greatly elongated sepals and three-parted corolla—all green—have decidedly the semblance of the second whorl of leaves always found on the flowering stems of the medeola.

V. Alluring Color.—Color is sometimes a trap.

There is a singular class of beings, half animal, half plant, in their ways of living—a fascinating, uncanny sisterhood—the insectivorous plants, which display marvelous ingenuity in the entrapping of their victims.

The bladder-wort, which abounds in stagnant ditches or ponds, is a member of this class, which has no apparent attractive powers. Yet Darwin says that one species has wonderfully constructed bladders, curiously like an entomostracan crustacean, and, strangely enough, these are the very animals most frequently killed by them.

Pitcher-plants excited the interest of scientists and travelers over a century ago, but the meaning and mechanism of these "plant-saloons" was only discovered within comparatively recent