Bij Professor Lindley. 



last winter are not observed in milder winters, in which rapid thaws 

 succeed severe freezing ; and, because it seems certain from what 

 we know of plants, that it is not the mere act of freezing, or un- 

 freezing, that destroys vegetable life ; it is necessary that the amount 

 of freezing should reach some unknown point, which seems to vary 

 in different species. Dr. Neuffer has shewn, (Edinb. New Phil. 

 Journ. 1830, p. 141,) that trees are frozen within certain limits 

 without apparent injury. In some trees, he ascertained that the 

 temperature was lowered to + 5°, or even to + without the 

 power of vegetation suffering ; so that the reduction of vegetable 

 tissue by cold into that state which is succeeded by an immediate 

 decomposition of the organic parts, varies in different species 

 according to their peculiar nature. 



In considering the various circumstances alluded to in this paper, 

 I was naturally led to inquire into the exact manner in which the 

 death of plants is caused by cold. Very little, however, is to be 

 learned upon this subject from the writings of physiologists. 



The common opinion is, that frost acts mechanically upon the 

 tissue of plants, by expanding the fluid they contain, and bursting 

 the cells or vessels in which it is enclosed. 



M. Gozppert, of Breslau, in a paper, originally read at the 

 meeting of German naturalists at Leipsig in 1829, briefly abstracted 

 in Okeris Isis for 1830, p. 497, and translated in the Edinburgh 

 Journal of Natural and Geological Science for 1831, p. 180, 

 denies that this supposed laceration of vegetable tissue by frost 

 takes place. He is represented to have stated, that the changes 

 which plants undergo, when they are killed by cold, do not consist 

 in a bursting of their vessels or cells, but solely in an extinction of 

 vitality, which is followed by changes in the chemical composition 

 of their juices. 



Professor Morhen, of Liege, in a paper, printed in the fifth 

 volume of the Bulletin de V Academic Royale de Bruxelles, has 



