640 THE POPULAR SCIENCE MONTHLY. 



waste all the precious summer weather in climbing a few feet, whereas 

 the same amount of longitudinal growth devoted to twining up a thin 

 stick would have raised them up to the light after which they are striv- 

 ing And as a plant exercises no choice, hut merely swings round till 

 it hits against an object, up which it will then try to twine, it seems 

 as if the inability to climb thick stems might be a positive advantage 

 to a plant, by forcing it to twine up such objects as would best repay 

 the trouble. 



In the classification of climbing plants, proposed by my father in 

 his book, he makes a subdivision of " hook-climbers." These may be 

 taken as the simplest representatives of that class of climbers which 

 are not twining plants. The common bramble climbs or scrambles up 

 through thick underwood, being assisted by the recurved spines which 

 allow the rapidly growing shoot to creep upward as it lengthens, but 

 prevent it from slipping backward again ; the common goose-grass 

 ( Galium) also climbs in this way, sticking like a burr to the side of a 

 hedge-row up which it climbs. Most country boys will remember 

 having taken 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 which I have described in twiners : they 

 simply grow straight on, trusting to their hooks to retain the position 

 gained. 



In some species of clematis we find a mechanism which reminds 

 one of a simple hook-climber, but is in reality a much better arrange- 

 ment. The young leaves projecting outward and slightly backward 

 from the stem may remind 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 the species of clematis given in Fig. 1 may 

 serve as an example of a leaf acting like a hook. The main stalk of 

 the leaf is seen to be 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. 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 which simple or true twin- 

 ing plants possess. Indeed, many species of clematis are actually 

 twining plants, and can wind spirally up a stick placed in their way. 

 And the same revolving 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 independently of the revolving 

 movement of the stem on which they are borne. 



* That is to say, the revolving movement is not sufficiently developed to be of practi- 

 cal importance. The same remark is applicable to the other cases in which I have spoken 

 of the absence of revolving movement in the growing parts of plants. 



