THE INNER ORGANIZATION OP TREES. 55 



Many plants are well known to be valuable as sources of 

 food and medicine ; and doubtless others exist around us 

 which are equally valuable, although at present the reason 

 OE THEIR CREATION IS uot SO apparent. One thing is clear, 

 that there is no such a thing in Nature as a plant which is 

 perfectly useless. Even weeds develope habits of care and 

 industry, which are called into exercise in effecting their 

 extirpation ; in addition to this, they undoubtedly perform 

 their allotted task in the great laboratory of I^ature, and 

 are the instruments by means of which nutritive matter is 

 extracted from the passing wind and the falling rain-drop, 

 which they deliver to the soil on which they finally decay. 

 A weed is, properly speaking, a plant out of place. Any 

 plant may become a weed if it is allowed to multiply to an 

 unreasonable extent, so as to prevent the growth of oth«r 

 plants which it is desirable to cultivate. 



I have spoken of the lessons of industry taught by the 

 vegetable world, but — the reader must pardon the digres- 

 sion — even the lifeless elements, the winds and waters, 

 what are these but the great labor-forces of Nature ? Those 

 clouds must be brought from yonder ocean to water this 

 thirsty landscape; these rocks must be pulverized and con- 

 verted into fruitful soils ; the winds that wander by you, 

 reader, are engaged in the discharge of these duties. See 

 the ocean at work, battering down the rocks along the 

 sea-shore ; and the rivers at work, transporting the mate- 

 rials of hills and mountains to the ocean. It is thus, after 

 myriads of ages, that the land and sea are made to change 

 places. "The sea," says Sir John Herschel, "is constantly 

 beating on the land, grinding it down, and scattering its 

 worn-off particles and fragments, in the state of mud and 

 pebbles, over its bed. Geological facts afford abundant 

 proof that the existing continents have all of them under- 

 gone this process, even more than once, and been entirely 

 torn in fragments, or reduced to powder, and submerged 

 and reconstructed." All this work is done by the winds 

 and waters. 



Surely in such a world, all labor directed to useful pur- 

 poses is honorable employment, and renders the laborer 



