PROTECTION OF PLANTS FROM FROST. 
267 
Magnolias, Photinias, &c., when standing in an isolated posi¬ 
tion to wrap them closely about with single, double, or triple 
mats, folding them tightly round the plant; this is erroneous for 
the reason we pointed out some little time back ; it is far better 
to allow the bottom of the covering (let the material be what it 
may,) project two or three feet beyond the circumference of the 
plant, as from the space so covered a constant radiation of heat 
is going on in an upward direction, which forms a strong re- 
pellant to the outward cold. So in the case of similar plants 
trained to a wall or other place, mats are nailed to the top, and 
securely fastened close to the bottom of the trellis, here also it 
would be preferable to continue the covering from the top of the 
plant in a slanting direction, to the extent of a yard beyond the 
base of the wall, or even if sufficient space could be afforded to 
unfasten the plant, and spread it in a horizontal position on or 
near the ground, and so cover it; this is only practicable in a 
few cases, but plants so treated would be surrounded by an at¬ 
mosphere quite as warm as though they were located in a green¬ 
house. It would be necessary to place the covering in such a 
manner as to throw off any accumulation of snow or very heavy 
rains, as the first might probably crush the plant, and the latter 
render the air about it much colder. Another point of much 
consequence is the danger incurred from too long a continuance 
of the covering, as also too hasty a removal: the first is to be 
avoided because of its weakening effect on the constitution of 
the plant, and the latter from the danger of a sudden transition 
from a dark and heated atmosphere, to the immediately opposite, 
as the confined state of the plant necessarily causes a relaxation 
of fibre, anything but favorable to it in its changed position. 
The action of frost on vegetable life may be familiarly explained 
in this way, the pores of the plant are from some pre-exciting 
cause, such as we have just mentioned, charged with too great 
a quantity of sap ; this fluid acting as a conductor, attracts a 
larger share of cold than would otherwise surround the plant, 
and in the mechanical action of freezing is enlarged, and so 
causes a disruption of the whole tissue of the plant. 
It should be borne in mind that plants under a covering of 
the kind mentioned, are subject to a very even and medium 
