THE INNER ORGANIZATION OF 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 

 OP THEIR CREATION is not 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 ex- 

 tirpation ; in addition to this, they undoubtedly perform 

 their allotted task in the great laboratory of Nature, 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 other 

 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 digression 

 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 converted into 

 fruitful soils ; the winds that wander by you reader, are en- 

 gaged 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 materials 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 scatteriug 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 undergone this process, even more 

 than once, and been entirely torn in fragments, or reduced to 

 powder, and submerged and re-constructed. 77 All this work 

 is done by the winds and waters. 



Surely in such a world all labor directed to useful purposes 

 is honorable employment and renders the laborer respectable. 



