86 



THE LEAF 



The actual motion is often faster than this, since the for- 

 ward movement is interrupted by retracings of the path 

 and by up and down or oblique deviations from the 

 level course. 



149. In case a twig or steni of another plant is encoun- 

 tered, the tendril bends round it and the clawed extremities 

 catch in the bark (Fig. 74, a). The several divisions of 

 the tendril, with their numerous hooks, lay hold on the 

 newly found support, and soon twist about it, while the 

 rachis shortens by coiling (Fig. 75), in the manner char- 

 acteristic of tendrils. 



150. The leaves of insectivorous plants. — The habitat 

 of insectivorous plants is chiefly marshes, like peat bogs. 



Those that the student will 

 be most likely to meet are 

 the Sundews and Pitcher 

 Plants. The commonest, 

 Sundew QDrosera rotundi- 

 folia)^ is a little plant, 

 generally acaulescent, with 

 its five or six rounded 

 leaves spread out horizon- 

 tally in a rosette from two 

 to four inches in diameter. 

 The leaves are thickly set 

 with hairlike organs (Fig. 

 76), each tipped with a 

 glistening drop of sticky 

 secretion. To judge from 

 the number of small insects, 

 mainly gnats and flies, usually found sticking on the leaves 

 of the Sundew, it seems not unlikely that the plants exer- 

 cise upon them some attraction, perhaps through an odor, 

 perhaps only by the brilliance of the clear secretion drops 

 shining in the sun, and the color of the purplish glands. 



151. The gland-tipped outgrowths are tentacles. The 

 marginal ones are the longest, and when fully spread out 

 in all directions, double the total diameter of the leaf. If 



76 



A leaf of Drosera rotundifolia, or 

 round-leaved Sundew (x2). 



