308 Observations upon the effects of Frost, 



From these facts, I think we must draw the conclusion, that the 

 fatal effect of frost upon plants is a more complicated action than 

 has been supposed ; of which the following are the more important 

 phenomena : — 



1. A distension of the cellular succulent parts, often attended 

 by laceration ; and always by a destruction of their irritability. 



2. An expulsion of air from the aeriferous passages and cells. 



3. An introduction of air, either expelled from the air passages, 

 or disengaged by the decomposition of water, into parts intended 

 exclusively to contain fluid. 



4. A chemical decomposition of the tissue and its contents, 

 especially of the chlorophyll. 



5. A destruction of the vitality of the latex, and a stoppage of 

 the action of its vessels. 



6. An obstruction of the interior of the tubes of pleurenchyma, 

 by the distension of their sides. 



These phenomena may be considered in part mechanical, 

 in part chemical, and in part vital. The two latter are 

 beyond our controul, and probably depend, in part, upon the 

 quality of fluid and organic matter, which may resist the action of 

 cold in different degrees, according to their various modifications ; 

 and, in part, upon specific vitality. Salt and water freeze at various 

 temperatures, according to the density of the mixture, 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 different degrees. 



The mechanical action of frost may however, undoubtedly be 

 guarded against to a great extent. It is well known, that the same 

 plant growing in a dry climate, or in a dry soil, or in a situation 

 thoroughly drained from water during winter, will resist much more 

 cold, than if cultivated in a damp climate, or in wet soil, or in 



