1818.] Death of Plants. 259 



quite black. Why do hay-ricks evaporate every morning and 

 evening for a short time in dry weather? because the dew excites 

 the evaporations, which precede the final extinction of life ; 

 nor can it be said that life is extinct, till all this evaporation and 

 consequent fermentation has ceased. I am firmly of opinion 

 that covering of a hay rick with a good thick tarpaulin would 

 be much more likely to stop its firing than putting it abroad, and 

 thus exposing it to fresh air and increased moisture. 



I shall now endeavour to inquire, in what vegetable life itself 

 consists, and what are the changes which plants undergo after the 

 vital power no longer enables them to resist the common law 

 of chemical affinity. 



In animals death has many percussors. It is the total stop- 

 page of the circulation of blood, the cessation of the animal and 

 vital functions consequent thereon, such as sensation and respi- 

 ration ; the smallest fibres grow rigid, the minutest vessels grow 

 into solid fibres, and are no longer pervious to the fluids ; the 

 greater vessels grow hard and narrow, and every part becomes 

 contracted, closed, and bound up ; and these symptoms increase 

 with the advance to old age. The most subtle fluids in the body 

 are intercepted and lost, the assimilation is weakened, and the 

 means of reparation by the glands prevented. Winslow remarked 

 that all the powers of art can scarcely determine where life ends, 

 and where death begins. The altered colour of the visage, the 

 loss of the animal temperature, and the rigidity of the joints, 

 nay, even the falling jaw, and the fixed eye, are not always sure 

 signs of death. The pulse of the heart may have apparently 

 ceased ; the glass applied to the mouth may be sullied by the 

 vapour of the body, and thus deceive ; or the person may be 

 living, and recover, though the glass has shown no signs of 

 breathing. The whole process is slow, and almost imperceptible ; 

 but it is still not so much so as the extinction of life in a vegeta- 

 ble ; for plants, like animals, unless destroyed by casualties or 

 disease, are doomed to die of old age. There may be~peculiar 

 circumstances confounding life and death in animals, but the 

 case i& not so generally. Vegetables may be said to be more 

 like insects, to exhibit a state of torpidity almost between life 

 and death. Thus flies, to all appearance, are drowned ; and yet 

 after two months, or more, being retained in this immoveable 

 condition will return to life, by the application of salt sprinkled 

 on them : and I have shown that a vegetable will suspend its 

 evaporation, when in the earth, and pass through a part of the 

 process of fermentation, and yet still be resuscitated, so as to 

 throw up suckers. The most extraordinary part of the pheno- 

 menon of a tree, is, that the longer the plants linger when dying, 

 the harder the wood grows : thus a tree that has all its limbs cut 

 oft*, and is stripped of its bark, and is then six months dyi;i<j;, aii 

 tins time the wood is hardening. But this matter is still in<>iv 

 sensible and evident in the hi asicas, and many herbaceous plant 9 , 



it 2 



