24 Effects of Frost on Plants. 
certain the cause of these phenomena, and the following is what 
observation has shown me. _ [I studied for this purpose more _par- 
ticularly the tissue of the apple. Each cell is filled with a small 
icicle which has in its middle a bubble of air. We know, that 
when water freezes, the crystals so arrange themselves, that the 
air separated from their mass by the solidification of the liquid is 
intercalated between their planes. This air also places itself in a 
mass of congealed water in a regular manner, the nature of which 
depends entirely upon that assumed by the crystals, as may be 
seen by freezing water in a cylindrical vessel, when the air-bub- 
bles always assume the form of a very long cone, terminated by a 
spherical cap. The augmentation of the volume of water is in 
great measure owing to this interposition of masses of air. All 
these effects take place in each cell of a frozen apple, which thus 
increases in size because each cell of its tissue becomes individu- 
ally larger. When thawed the cell recovers itself by the elasticity 
of its vegetable membrane, and frozen fruit becomes, as we know, 
very much shrivelled. Each cell, therefore, acts like a bottle of 
frozen water, only there is no bursting, because the membrane is 
extensible.’ But when plants, easily killed by cold, are exposed 
to so low a temperature as that just described, it is to be feared 
that phenomena actually connected with the dentranticn of veget- 
able life may be intermixed with others, which merely indicate the 
principal effects of cold upon vegetable matter already dead. For 
the purpose of judging how far this conjecture is well founded, I ~ 
have carefully examined the post mortem appearances of several 
plants killed by exposure to a temperature artificially reduced only 
to from 28° to 30° Fahrenheit. These observations, while they 
have confirmed the general accuracy of Professor Morren’s state- a 
ments, have led to other conclusions, which also appear impor- 
tant.” In these cases Dr. Lindley remarks that he did not find 
the vesicles of cellular tissue, separable from each other, even in 
the most succulent species, whence he concludes that this result 
is not essentially connected with the destruction of vegetable life, 
but is the effect of a great intensity of cold upon the tissue. In 
several instances, however, he found the tissue lacerated, as if by 
the distension of the fluid it had contained; and sometimes he 
found the cells so eens broken up, that it was difficult to 
tain a thin slice for examination. The young shoots of several 
species of Erica, and of some other plants, were shivered into a 
