THE PLANT AND THE ANIMAL 275 



The leaf will immediately fold up and only reopen when 

 all trace of the food supplied has gone. The catch- 

 fly, as we have already said, lives in the marshes of 

 North America, but some of our own marshes provide 

 us also with a plant, which, though related to the catch- 

 fly, yet attains the same end, i.e. feeds upon insects, 

 by means of a somewhat different adaptation. This 

 plant is the Sundew (Drosera). Its small leaves are 

 covered with a certain kind of hairs, the ends of which 

 secrete drops of a viscid liquid. This liquid used to 

 be taken for dew, hence the name of the plant. The 

 insect which imprudently settles upon the leaf sticks to it. 

 The leaf then quickly manifests an extremely curious 

 kind of movement. The hairs from all sides tend 

 towards one and the same point, where the imprisoned 

 animal lies ; the glands at the tips of the hairs secrete 

 their sap profusely, and it dissolves the solid particles 

 of the nutrient substances, transforming them into a 

 condition in which they become easily absorbed by the 

 cells of the hairs. When the food is completely absorbed 

 the hairs expand again and are ready to meet another 

 visitor in the same way. The large peculiar leaves 

 of Nepenthes, Sarracenia, and Cephalotus found at 

 lower latitudes are not less curious, as well as the 

 minute leaflets of the bladderwort {UUricularia) in 

 our streams and ponds. One part of the leaf of the 

 three former plants develops into a pitcher, which 

 in the case of Cephalotus is, moreover, covered 

 with a lid, while in the bladderwort the finely sub- 

 divided submerged leaves are provided with similar 

 little organs. The pitchers were long ago observed to 

 contain a liquid. Formerly this liquid was thought 

 to be water, and only recently it has been proved to 

 possess the property of dissolving solid organic food 

 substances. Closer investigation of these pitchers 

 has revealed in them very complicated adaptations 

 for catching insects. They contain parts which secrete 



