EXTERNAL CONFIGURATION OF PLANTS. 183 



leaves offer but little resistance to the air. When 

 these things are taken into consideration, it may well 

 be that the pine is much better adapted for resist- 

 ing the force of the wind than ordinary trees where 

 the primary stem divides into numerous large 

 branches. 



The ramifications of the root are of the utmost 

 imiDortance in relation to wind-pressure. While ex- 

 tending the area of absor^Dtion, the branches of the 

 root enable the plant to take a firm grasp of the 

 soil. A turnip-like root would be quite incapable of 

 keeping in position a plant that exposed a large 

 surface to the wind. The adventitious roots of the 

 screw-pine, which form a pile of props surrounding 

 the base of the stem, and give the tree a conical 

 outline, must greatly increase the tree's stability by 

 extending the base on which it stands. The mode 

 of attachment common in marine plants is quite 

 unsuitable for those which grow among earth. A 

 sea-weed does not bury its roots. In many AJg(e 

 the base of the frond simply expands into an 

 adhesive disc, which attaches itself by a kind of 

 cement to stones. A sucker-like root of this kind, 

 adhering to the friable earth, would give no stability 

 to a terrestrial plant. The adhesive discs at the ends 

 of the tendrils of the Virginian-creeper show that 

 this plan may be of service in climbers where the 

 suckers are attached to rocks or walls, but it would 

 be useless as a means of attachment to ordinary soil. 



The geologist starts with a plane of marine denu- 

 dation, and traces back to the erosive action of 

 water, mountains, valleys, and all the existing 

 features of the land-surface. In like manner the 

 botanist, starting from the primitive spherical form, 

 may yet succeed in showing that all the varied 

 patterns of the vegetable world have been cut out 

 by the operation of natural forces. Natural agencies, 

 acting on organisms originally spherical, might carve 

 them almost into any shape. It is quite conceivable, 

 therefore, that the forms of existing plants, varied 



