DESTRUCTION OF PLANTS BY FROST. 



any change in the curious double-headed bodies, in form resembling dumb-bells, found in 

 the vessels of Euphorbias, and supposed to be a state of amylaceous matter, because iodine 

 colors them violet; they appeared to me to be in precisely the same state before and after 

 the plant was frozen to death. M. Payen, however, denies that any starch whatever is 

 lost in frozen potatoes ( Comptes rendus, vi. 345;) but as only a small part of his impor- 

 tant treatise on amylaceous matter has reached this country, I am unable to state in what 

 way he explains the action of cold upon this substance. 



'* Finally, it appears that frost exercises a- specific action upon the latex, destroying its 

 power of motion. If, as Prof. Schultz supposes, this is the vital fluid of plants, such a 

 fact would alone account for the fatal effects of low temperature. In all the cases I have 

 observed frost coagulates this fluid, collecting it into amorphous masses. In Stapelia, 

 where the laticiferous vessels are easily found, the latex itself is so transparent, that it is 

 difficult to perceive it in a living state, even with the best glasses; but after freezing it is 

 distinctly visible, resembling half coagulated water. In the Hibiscus above mentioned, 

 the stem is covered with long, rigid, simple hairs, filled with a plexus of capillary lati- 

 ciferous vessels of extreme tenuity, but in which the motion of the latex may be seen 

 beautifully with the one-eighth of an inch object glass of an achromatic microscope. Upon 

 being thawed, after freezing, all this apparatus is found reduced to some misshapen sepa- 

 rate sacs of fine grumous matter, in which no motion can be detected. That these vessels 

 lose their vitality after freezing, may indeed be seen without the aid of a microscope; for 

 if a stem of a Ficus elastica, or a Euphorbia, or any such plant, which discharges an 

 abundance of milk when wounded, be first frozen, and then thawed, no milk Mill follow 

 the incision. 



" 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 distention of' the cellular succulent parts, often attended by laceration, and al- 

 ways by a destruction of their irritability. 



" 2. An expulsion of air from the seriferous 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 chloro- 

 phyll. 



" 5. A destruction of the vitality of the latex, and a stoppage of the action of its ves- 

 sels. 



" 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 control, and probably depend, in part, upon the 

 quality of fluid and organic matter, which may resist the action of the 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 30"; 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 indefinitely modified. Mill resist 

 the action of cold in very different degrees. 



he mechanical action of frost may, hoM'ever, undoubtedly be guarded agains 

 extent. It is well known, that the same plant growing in a dry climate, or in 



