Page:Popular Science Monthly Volume 65.djvu/428

424 with it here, as in the stomachs of animals, a coagulating principle, a rennet. In some manner difficult to guess the shepherds of the Alps learned years ago that the leaf of the butterwort placed in fresh milk would cause it to thicken rapidly, and to this day they use these leaves rather than the animal extract in the making of curd for cheese.

The sun-dew (Drosera) is one of the best known of the insectivorous plants of this class, both because of the wide distribution of the ninety species over the world and on account of the detailed and patient study of it which was made by Darwin, whose Insectivorous Plants' is a rich mine of information for any one interested in