Killing of Plant Tissue by Low Temperature 149 



color changes often take place, due to chemical changes when the 

 coloring matter comes in contact with other substances from other 

 cells. Death^ can often be detected by these color changes. In the 

 case of certain buds, and especially the stem and root tissue of hardy 

 trees, the changes indicating this sort of death from cold can not 

 be detected so soon after thawing, but are very characteristic, the 

 tissue showing the watery, brownish appearance in a few hours after 

 thawing. In all cases water is very rapidly lost from tissue killed 

 in this way. Thus Goeppert^ has shown that 24.25 grams of frozen 

 canni. leaves, which on thawing proved to be dead, lost when kept 

 for sc days in the open air near a warm stove, 21.25 grams, while 

 the same weight of live canna leaves lost in the same length of time 

 only 11.27 grams. When the killing temperature is barely reached, 

 not all of the tissue is likely to be killed, but often there will be spots 

 of dead tissue with live tissue adjoining. It has been observed by 

 Sorauer and others, that the number of dead cells does not increase 

 beyond those that are easily observed to be dead a short time after 

 thawing. However, it requires longer for death to be plainly ob- 

 served in the case of some tissues than others. As mentioned above, 

 the tissue of the sap wood and cortex does not show plainly whether 

 or not it is dead as soon as does the tissue of leaves and buds. Sorauer^ 

 found that epidermal tissue is slower in showing death after thawing 

 than other tissues. 



REVIEW OF THE LITERATURE ON FREEZING TO DEATH 



In this paper the term freezing to death will be used as it was 

 used by Miiller-Thurgau, only when referring to the phenomena 

 just described. While some early observers were of the opinion that 

 plants have the ability to generate heat within their tissue and thus 

 avoid severe freezing, the early Greek philosophers, observing the 

 presence of ice within the plant tissue and not knowing of the cellu- 

 lar structure, were of the opinion that the injury was due to rending 

 and mashing organs by the ice formation. Du Hamel and Buffon"* 

 were among the first to present a theory of the cause of death from 

 cold based on a partial knowledge of cellular structure. They be- 

 lieved killing to be a rupturing of the cell walls due to the expansion 

 accompanying ice formation. 



'Mollach, UntormirhunK tibcr dnn. otn, 1897. Book. (Blbl. No. 75); Miillor-ThurKiui, 

 Landw. Jahrb. Vol. l.^>. p. 4r,3, l.sso. (Hlbl. No. 78). 



*Ueher die WttriiuHjntwlckolunK, I'tc. Hook. 1830. (Hlbl. No. 44). 



*Landw. Jahrl),, Vol. 35, pp. 4(i0-fi25. IVMW. (Hlhl. No. I0r>). 



^Mera. d. I'Acad. Hoy. Scl.. Parl.s, 1737, pp. 27a--'98. (Illbl. No. 30). 



