86 VITAL ACTIOKS. 



quality of fluid and organic matter, wliich may resist 

 the action of cold in different degrees, according to 

 tlieir various modifications, or else upon specific vi- 

 tality. Salt and water freeze at different tempera- 

 tures, according to the density of the mixtures, from 

 4° to 27° ; oil of turpentine at 14° ; oil of bergamot 

 at 23° ; vinegar at 28° ; milk at 30°.; water at 32° ; 

 olive oil at 36° ; oil of anise at 50° ; and it is not to 

 be doubted that, in like manner, the fluid contents of 

 plants, which we know are infinitely modified, will 

 resist the action of cold in very difierent degrees.* It 

 is recognised indeed as a general law, that the difli- 

 culty of freezing water is in proportion to its density. 

 112. The effect of congealing the aqueous particles 

 contained in plants is, in itself, sufficient to cause such 

 a derangement of function as may end in death, and 

 the other supposed causes may be left out of conside- 

 ration. It will thus follow that, omitting differences 

 arising out of the peculiar nature of difierent species, 

 plants will suffer from frost in proportion to the abun- 

 dance and fluidity of their secretions ; those whose 

 tissue is driest, and whose secretions are most dense, 

 being the most capable of resisting frost. Hence young 

 shoots are destroyed by a degree of cold which does 

 not affect old shoots of the same species ; and hence, 

 also, the diminished capability of "unripe" shoots, or 

 of plants growing in wet situations, or of trees when 



* See a paper on frost in the Transactions of the Horticultural So- 

 cieiy, new series, vol. ii. p. 308. [A copious abstract of Dr. Lindley'a 

 highly interesting memoir upon this subject will be found in the Aine- 

 rican Journal of Science and Arts, for March, 1840. G.] 



