HORSE-TAILS 213 



water. Many a potato field knows it, and a 

 mile from the pond it grows, if it does not flourish, 

 in dry stone brash nine hundred feet above the 

 level of the sea. 



Driven from the lake's edge by flowering plants 

 of a new model, the jointed canes, with their old- 

 world whorls of twigs for leaves, have the acre of 

 water all to themselves, so far as rooted vegetation 

 is concerned. And what are those minor parts 

 that I have just written down as ' twigs for 

 leaves ' ? If we seize the plant and pull both 

 ways at its trunk it comes apart at a joint, the 

 lower or socket part of which is fringed with tiny 

 teeth. These tiny teeth are the leaves all else 

 is trunk and branches. But because the plant's 

 leaves are so poor, all the rest of its anatomy does 

 leaf duty by remaining green and full of stomatse 

 wherewith to take food from the air. And the 

 trunk and each branch seems to get the idea some 

 dozen times in the course of their length that they 

 really are deciduous leaves. For the socket and 

 joint arrangement is like nothing else in nature 

 so much as that by which the leaf is cast from 

 the end of the twig when autumn comes. 



If we set out to make a model of the horse-tail 

 we should be compelled to do it in steel. Nothing 

 else could be drawn so thin and preserve its 

 rigidity. The stiffening material that the plant 

 employs for its airy structure is flint in the form 

 of silicic acid. The skeleton of every twig, nay, 

 every cell, is composed of this enduring substance, 



