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. Lindley’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. Geeppert, 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 Liége, in a paper printed in the fifth Vol. 
of the Bulletin de UV Acad. Royale de Bruzelles, has published 
some exceedingly interesting observations upon this subject. 
Like M. Geppert, 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- 
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