66 THE HARMONIES OF NATURE. 



increases in the same proportion as the size of the crown ; but 

 the palms of the tropical zone have a different growth, as with- 

 out any very perceptible increase in the diameter of their stem, 

 they rear their colossal fronds higher and higher into the air. 

 Yet, in spite of their comparatively slender trunks, and their 

 towering stature, which is surpassed by that of but few other trees, 

 they as effectually withstand the pressure of the storm as our 

 firs or oaks, or as the dicotyledonous giants of their own zone, 

 for their fibrous cells, which unite a remarkable degree of tough- 

 ness with a considerable pliability, are interlaced so firmly at 

 or near the surface of the trunk, where they are most compactly 

 arranged, that they are enabled to bend without breaking, to 

 bow down before the hurricane, and to rise again as soon as its 

 fury has passed. 



In the climbing or creeping-plants, whose thin and delicate 

 stems are quite out of proportion to their weight, this want 

 of self-supporting strength is compensated in various ways ; 

 so that, in spite of their apparent weakness, they are able to 

 carry their heads as high as if they rested on colossal trunks. 

 Some of them embrace other plants by growing in a spiral 

 direction, as, for instance, our beans and hops ; others, like the 

 ivy, emit from their stem short aerial roots, which serve as 

 hold-fasts in the crevices of old walls or trees ; and others, again, 

 like the vine, climb upwards by means of tendrils, which, grow- 

 ing out of the axillae of the leaves, wind round neighbouring 

 objects, and prop the plant as it ascends. 



The tropical rattans, those remarkable climbing palms, whose 

 rope-like stems often consist of a couple of hundred joints, each 

 two or three feet long, and bearing at every knot a feathery leaf, 

 rest so firmly upon the branches of the trees by means of the 

 strong barbed thorns with which the petioles of their leaves are 

 armed, and interlace themselves so frequently, that it is extremely 

 difficult to detach them from their hold. Thus supported, they 

 climb to the summits of the highest forest trees, and while it is 

 impossible to distinguish their creeping stems from the intricate 

 tangles of the matted underwood, their palm-like topes expand 

 in the sunshine, the emblems of successful parasitism. 



Other tropical climbers, again, have neither thorns nor 

 tendrils to support them, but, as soon as they have found a stay 

 in some neighbouring tree, they begin to extend over its surface 



