Volume 9 Number 2 



The Plant World 



9t iflaja^inc of popular ^otanp 

 FEBRUARY, 1906 



THE OCCURRENCE OF ICE IN PLANT TISSUE. 



By K. M. Wiegand. 

 Cornell Uiiiz'crsity. 



It is a commonly observed phenomenon that when the tempera- 

 ture falls below the zero point centigrade many plants undergo a 

 change in texture as well as to some extent in form and color. 

 When the temperature again rises these same plants are afifected 

 in a definite manner. Either they return to their normal condi- 

 tion, or they immediately wilt and in a short time inidergo almost 

 complete disintegration. An examination of the interior of such 

 plants, while still rigid, discloses the presence of ice crystals, 

 usuallv in large numbers, in some cases appearing to almost fill the 

 leaf, stem or bud, in others occupying certain definite regions 

 in the tissues of these organs — in other words, the organs are 

 " frozen." 



Although the fact that plants freeze and are often killed by 

 freezing" is well known to every one, the details of the process are 

 known to Imt very few, as most text-books give little attention to 

 the subject. It is not the object of this paper to present the re- 

 sults of many new investigations, but to bring together in acces- 

 sible form what is already known of the subject. 



The early Greek philosophers gave the matter their attention 

 in an attempt to account for the death of plants by cold. Not 

 understanding the cellular structure of organisms, they believed 

 the injurv due to the rending and mashing of the various organs 

 bv the ice-formation, which they correctly discovered often oc- 



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