By Mary Treat
IX.—THE UTRICULARIA.
It seems strange that innocent-looking plants should capture and kill animals; but this is really what the Bladderworts (Utricularia) are all the time doing. They grow in ponds and swamps, some species in deep, still water, others in shallow ponds.
Fig. 1 shows a portion of the stem of Utricularia clandestina, natural size. The little bladders are so nearly transparent, that on bringing them under the microscope, or even under a good lens, you can see the numerous creatures that they have captured, some partly consumed, others still alive.
The bladders on these curious plants remind one of some of the Entomostracans which Mr. Wells described in his fourth paper. Look at Chydorus sphericus for instance, and then at the magnified bladder (Fig. 2) in this article. The branched horns at the mouth or entrance have very much the appearance of the antennæ of some of the minute animals, and the stem when it is attached to the main branch may be likened to a tail. But the way in which they capture and devour the pretty little creatures that come within their grasp makes them appear, even more than they look, like wicked animals.
FIG. 1. PORTION OF A STEM OF UTRICULARIA
CLANDESTINA; NATURAL SIZE.
I have found almost every swimming animalculæ with which I am acquainted, caught in these vegetable traps; and when caught they never escape. Their entrance is easy enough; there is a sensitive valve at the mouth of the bladder, which, if they touch it, flies open and draws them in as quick as a flash. These downward-opening bladders not only entrap animalculæ, but, more wonderful still, the strong larvæ of insects. The larvæ most frequently caught are those of the mosquito and chironomus. Often the mosquito is caught tail first—the entire body inclosed and the head left sticking out. It always looks as if the victim might walk or wriggle out, but it never does; and you may be sure that it never backed in there of its own accord.