AMERICAN INSTITUTE. 



271 



rces. Cherries, plums, apples, &c., may be made to produce the same 

 results. 



The leaf of a tree is merely the expansion of the bark, and acts upon 

 the atmosphere in the same manner that the root does upon the soil, and it 

 is an expansion of the bark likewise, changed at its extremity into a spongy 

 mass, which possesses the power of absorbing a very large quantity of water, 

 and extracting the gases which it contains for the benefit of the plant, 

 besides soda, lime, potash, and even silica. But decidedly the most impor- 

 tant function that roots possess, is their power of selecting those matters 

 from the soil best calculated to maintain their growth and healthy con- 

 dition. You may present to the roots of a plant, acetate of lime, or 

 strontia, in a lic(uid form, and they will not absorb either ; if they did, 

 immediate death would ensue. Men and animals do not possess this pow- 

 er, and often swallow, unwittingly, substances that prove fatal. Sheep will 

 eat various poisons, such as the five-finger vine, laurel, &c., and men, opi- 

 um, arsenic, &c. Water appears to possess the power of selecting ; if you 

 present nitrogen, oxygen, and carbonic acid gas, it will give preference to 

 the latter, and absorb it first. 



Boots in my mind are constituted to choose from the earth, and give 

 decided preference to those matters which are the most essential to their 

 natures, and if they are not there, the plant will no doubt admit matters 

 that may be injurious. These however are never found in the natural 

 soil or climate of any plant, and therefore the roots cannot encounter any 

 poison, unless administered by man. I have invariably advanced the theory 

 that all plants throw off excretory matters, which has often been denied by 

 those with whom the subject was discussed. To satisfy myself, last sum- 

 mer, I caused a few kernels of wheat to germinate in a powder of perfectly 

 pure chalk, and found in it afterwards aceate of lime, showing that they do 

 excrete. Yet notwithstanding, by experiments for several seasons, I am 

 unable to satisfy myself that there is a positive benefit to be obtained by a 

 rotation of crops, which I have always advocated and practiced faithfully 

 heretofore. Last year I plowed up a clover field, which had grown that 

 crop successfully for three years, and sowed it to rye ; the yield was splen- 

 did, and I at first attributed it to the excrementitious substances thrown 

 ofi" by the clover. But upon thoi'oughly examining the soil, found it full 

 of decomposing roots, and was obliged, I must confess unwillingly, to yield 

 my favorite theory, and give the credit where it was justly due. The next 

 field, with a fine growth of rye sown the previous fall, was plowed under, 

 and sown with oats ; this crop was equal in quantity and quality to the rye 

 or clover, the rye giving to it the requisite quantity of green manure, it not 

 yet having had growth enough to throw off any large amount of excrement. 

 We have too few experiments upon this very important subject to permit 

 us to decide with any degree of certainty ; I intend however to continue 

 them, and will from time to time report progress, as the earth continues to 

 reveal the phenomena of her vegetable mysteries to my experiments upon 

 her bosom. 



