276 



\Vhv»t organ 

 hrst £tils ? 



Analogy be- 

 tween vegpta. 

 ble and ani- 

 mal orsuns. 



Experiments 

 may be made 

 ou trees that 

 cannot on ani 

 mjis. 



Oigans of re- 

 getdbles and 

 animals com- 

 pari'd. 



PARTS OF TRVES FIRST IMPAIRED BY AGC. 



expprimertts on grafted tree«, from vhicli I inferred, that 

 eath vitiifty ifm\ be proprtfi^ated vvilli suct'esfe duti-rtg a linttifwl 

 perrfiifl toftly; ^hd thut the grkft, or other dttacli^d part of 

 an old tree, or oM variety, csin never form that, which ean 

 with propriety be called a young- tree. 



1 have subsequently endtavonved to ascertain which, 

 amorfg the varioiis> orga-ns that compose a tree, tirst fails to 

 execute its office, and thus tends to bring on the incurable 

 debility of old ag^e; and the result of the experiments ap- 

 pears sufficiently interesting, to induce me to commuiiicat* 

 an account of them. 



Whatever difference exists between the functions of ani- 

 mal and vegetable life, there is a very obvious analogy be- 

 tween some of the organs of plants, and tliose of animals ; 

 and it does not appear very improbable, that the corres- 

 pondent organ, in eacli, may first fail to execute its office J 

 and satisfactory evidence of the imperfect action of any 

 particular organ can much more easily be obtained in the 

 vegetable than in the animal world. For a tree may be 

 composed, by the art of the graiter, of the detached parts 

 of many others ; and the defective, or efficient, operation, of 

 each organ, may thus be observed with the greatest accu- 

 racy. But such observations cannot be made upon animals ; 

 because the operations necessary cannot be performed ; and 

 therefore, though th«re would be much danger of errour in 

 incautiously transferring the phenomena of one class of 

 organized beiu^ to another, I conceive, that experiments 

 on plants may be, in some cases, useful to the investigator 

 of the animal economy. They raay direct him in his pur- 

 suits, and possibly facilitate hi* inquiries into the immediate 

 causes of the decay of animal strength and life; and on a 

 subject of so much importance to mankind, no source of 

 information should remain unexplored, and no lights, how- 

 ever feeble, be disregarded. 



jVatuialists, botl: of ancient and modern times, have con- 

 siderf^d the structure of plants as an inveision of that of 

 animals; and liave compated the roots to the intestines, and 

 the leaves to the lungs, of animals; and the analogy be- 

 tween the- yegetablt' sap and animal blood is very close 

 and obvious..,. Tb€-. experiments also, of which I have at 



different 



