16 NATURAL HISTORY READER. 



advantage of this burr-like quality of Galium in making 

 sham birds' nests, the prickly stems adhering together in 

 the desired form. Such plants as the bramble or Galium 

 exhibit none of the swinging-round movement of climbers : 

 they simp]\- grow straight on, trusting to their hooks to re- 

 tain the position gained. 



2. In some species of clematis we find a mechanism 

 which reminds one of a simple hook-climber, but is in real- 

 ity a much better arrangement. The \oung leaves project- 

 ing outward and slightly backward from the stem may re- 

 mind us of the hooked spines of a bramble, and, like them, 

 easily catch on neighboring objects, and support the trailing 

 stem. Or the leaf of a species of clematis may serve as an 

 example of a leaf acting like a hook. The main stalk of 

 the leaf is bent angularly downward at the points where 

 each successive pair of leaflets is attached, and the leaflet at 

 the end of the leaf is bent down at right angles, and thus 

 forms a grappling apparatus. 



3. The clematis does not, like the bramble, trust to mere 

 growth to thrust itself among tangled bushes, but possesses 

 the same powers of revolving in search of a support wdiich 

 simple or true twining plants possess. Indeed, many species 

 of clematis are actually twining plants, and can wind spi- 

 rally up a stick placed in their way. And the same revolv- 

 ing movement which enables them thus to wind spirally 

 also helps them to search for some holding-place for their 

 hook- or grapple-like leaves, and in many species the search 

 is carried on by the leaves swinging round, quite independ- 

 ently of the revolving movement of the stem on which they 

 are borne. 



4. If a leaf of a clematis succeed by any means in book- 

 ing on to a neighboring object, the special characteristic of 

 leaf-climbing plants comes into play. The stalk of the leaf 

 curls strongly over toward the object touching it, and clasps 

 it firmly- It is obvious how great is the advantage thus 



