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Page:Popular Science Monthly Volume 49.djvu/707

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DOGBANE AND MILKWEED.

edge, into five slender points. Its deep pink veining suggests nectar," and the insect visitor is not disappointed, for at its base are five nectar-bearing glands. These stand in a ring around the pistil, and in a larger circle, outside the ring of honey glands, are the five stamens. The anthers stand erect, and in shape are like arrow or spear heads. Corresponding to the two points at the base of a spear head, there are, at the base of each anther, two little hard horns, and the stamens ring so closely about the pistil that horn is pressed against horn all around the circle.

On the inside of the corolla, near its base, are five triangular callosities, with their points up. These are placed in such a way as to alternate with the stamens, and stand a little below them, so that the two hard points at the bases of two neighboring anthers, and the hard tip of the callosity—three little horns—come together like the teeth of a trap. There are no fewer than five places inside the flower's cup where these traps are set, and inside the circle of traps are the glands which contain nectar. The flower is visited by bees and flies.

The insect caller must run his proboscis in between the long anthers, and just above the horny excrescences on the corolla. When he attempts to withdraw, after drinking his fill, the three points lock together, like the jaws of a trap, holding the tip of his proboscis in durance vile. If the winged captive is big and strong, he gets free, with a long and a vigorous pull. But small flies are often held prisoners till they die, probably from starvation. Sometimes one may see three or four of these hapless victims on one full-blooming plant of spreading dogbane.

Among the prisoners one may often see a little summer fly of dudish aspect, with body ringed with alternate bands of bronze and gold, and wings of gauze shot with opaline colors. To what end is this bright little fellow sacrificed? Held as he is by the tip of his proboscis, his body does not come in contact with the plant, and hence it can not be digested by the vegetable juices, as are the corpses of the sundew's victims. The dogbane is apparently unable to furnish any adequate justification for his taking off.

There is another variety of dogbane, the Indian hemp, orApocynum, cannabinum, which bears smaller blossoms than the androsæmifolium, blooms somewhat later, and is more widely distributed over the country. This flower has no callosities in its corolla, sets no snares for insect victims, and is apparently quite innocent of the crimes which one is inclined to lay to the charge of its first cousin.

The common milkweed (Asclepias cornuti) also imprisons insects, which sometimes die in captivity, and do no apparent good to the plant by their deaths. They have, however, invited misfortune, for though the milkweed is rich in honey, and is visited