Prof. J. Le Conte on the Freezing of Vegetables. 205 
“6. An obstruction of the interior of the tubes of pleurenchyma 
(woody fibre) by the distension of: their sides.”* 
t will be observed, that the phenomena are partly mechanical, 
partly chemical, and partly vital. S@ far.as the mechanical effects 
are concerned, it is very plain, that whatever increases the amount 
of moisture in the plant, augments the liability to laceration of 
tissues, when freezing supervenes. In relation to the chemical 
and vital phenomena, it is sufficiently obvious, that the effects of 
cold must vary with the condition of the fluids in the plants. 
The well-known evil influence of cold in the spring, or after a 
warm spell in winter, is, probably, referable to the augmented 
Susceptibility which seems to attend the growing state. It is dif- 
ficult to say whether this increased susceptibility to the action of 
cold, is due to an alteration in vital sensitiveness, or to a prone- 
t and cause. 
i deed, the proof of this may be considered two-fold; both neg- 
dive and positive. For it is well known that many tropical ex- 
Otics are destroyed by a degree of cold considerably above the 
freezing point of water when, of course, their sap cannot be in 
state of congelation: while, on the other hand, as I have en- 
deavored to show in this memoir, the juices of other plants are 
obviously and repeatedly frozen without the slightest injury to” 
© powers of vegetation. : : 
The analogy between animals and vegetables seems to be, in 
this respect, almost as perfect as it is remarkable. A degree of | 
cold which alsolutely freezes the fluid contained in their struc- 
tures ts not equally fatal to all plants. As among animals, each 
Species of plant is adapted to endure a certain range of tempera- 
ture, which determines, with more or less precision, the limits of — 
lls geographical distribution. The fact that vegetables are less 
Susceptible to the injurious influence of cold when in a dor- 
RE ce gen he 
, Vol xxxix, p. 18, et se 5 2 ‘ 
t At is hes probable that ee afar effects of cold upon growing plants, os 
be, in part, due to the sudden stoppage of the changes which attend the wo 
active cell-development. It is —— ata oer ae any ne eed 9 of thi 
a period, would lead to rapi chemical . ome 
Well-known fact that, a ened potatoes, Phe starch is converted into oun 
on reer that important chemical changes may be brought about by the influ  . 
. 
ny ceri 
