22 Effects of Frost on Plants. 



return of spring, when the sap is attracted upwards by the bud- 

 ding leaves. The winter, therefore, is the dry season of such 

 plants, and, for that reason, the period in which they are least lia- 

 ble to the effects of frost. But if any unusual circumstance alters 

 this habit, the capability of resisting frost is altered with it ; and 

 thus the plants mentioned in the instances lately quoted, stationed 

 in warm sheltered situations, were stimulated prematurely into 

 growth, their stems were filled with fluid, and they were, in con- 

 sequence, affected by frost in a much greater degree than when, 

 from the coldness of a station, they were kept in their ordinary 

 winter condition." 



But the concluding portion of this memoir is that which pos- 

 sesses, perhaps, the most general interest : this is the enquiry into 

 the exact manner in which the death of plants is caused by cold. 

 To give our readers a just idea of Dr. Lind ley's observations on 

 this subject, we are under the necessity of making copious and 

 lengthened extracts from this part of the memoir, as it will not 

 bear much condensation. 



" The common opinion is, that frost acts mechanically upon the 

 tissue of plants, by expanding the fluid they contain, and bursting 

 the cells or vessels in which it is enclosed. M. Gceppert, of Bres- 

 lau, in a paper originally read at the meeting of German natural- 

 ists at Leipsig in 1829, briefly abstracted in Oken^s Isis, for 1830, 

 and translated in the Edinburgh Journal of Natural and Geolo- 

 gical Science, for 1831, p. 180, denies that this supposed laceration 

 of vegetable tissue takes place. He is represented to have stated, 

 that the changes which plants undergo, when they are killed by 

 cold, do not consist in a bursting of their cells or vessels, but solely 

 in an extinction of their vitality, which is followed by changes 

 in the chemical composition of their juices. 



" Professor Morren of Liege, in a paper printed in the fifth Vol. 

 of the Bulletin de VAcad. Roy ale de Bruxelles, has published 

 some exceedingly interesting observations upon this subject. 

 Like M. Goeppert, he denies the truth of the statement generally 

 made, that frost produces death in plants by bursting their vessels ; 

 and he assigns the effect to other causes. His more important 

 conclusions are — 1. That no organ whatever is torn by the action 

 of frost, except in very rare cases when the vesicles of cellular 

 tissue give way, but that the vesicles of plants are separated 

 from each other without laceration. 2. That neither the chlo- 



