AGRICULTURAL METEOROLOGY. 139 
shrubs in open grounds. Where the risk is slight it is preferable to 
ineur it rather than to use covering; but where the plant is unquestion- 
ably tender there is no alternative. For deciduous plants, straw bound 
neatly around them is as good and as unobjectionable as any method. For 
evergreens an old barrel or wooden structure is best. 
When out-door coverings are used they shouid not be removed too 
early in the spring, becanse the plant will be more susceptible to changes 
of temperature than if it had been wholly exposed to the action of the 
weather.* 
The editor of the Horticulturist says: “We indorse emphatically 
B. M.’s treatment, because we have tried it many times with entire suc- 
cess.” In regard to out-door plants, more injury is sustained from too 
much covering than from severe weather, and often plants are covered 
which do not require protection.” 
Mr. E. Alesworth, of Peterboro, New: York, was in the habit of using 
boxes, casks, pails, pans, and cloths to protect plants in frosty nights. 
One very cold night be covered one plant with a basket; in the morning 
nearly every other plant was killed. It is well ‘known that if, on the 
approach of a frosty night, the wind still continues to blow, there is not 
frost enough to do much injury; but if the wind goes down with the 
sun, and is succeeded by a calm, the consequences are very severe to 
young flowers and garden plants. Any covering only upon the sides 
or ends will create a draught in the stillest night; and this was the case 
with the basket. Alesworth has ever since placed boxes, &c., at inter- 
vals, and laid boards on the top of them, leaving both sides wide open, 
and he never loses a plant. t 
Mr. J. Griffith states that the action of frost in lifting fence-posts from 
- «the ground may be prevented by casing the lower ends of the posts 
with boards, or, far better, with tile of the right size. This casing will 
be affected by repeated freezing and thawing, but the posts will remain 
unmoved. t 
INFLUENCE OF THE COLOR OF WALLS UPON ESPALIERS. 
¥ 
4 
The cultivators of trees believe that the coloring of walls increases 
the heat received by espaliers, or wall-trees. A black wall gathers more 
heat, by the absorption of solar rays, than one painted white, which 
reflects these rays; a black wall would therefore be preferable for vines 
and trees bearing fruits with stones, which require a tolerably strong 
heat; whereas, a white wall would be most suitable for the trees which 
bear fruits with seeds. 
The principle is correct, but the conclusion is erroneous, for the real 
action of the coloring of walls upon espaliers is not yet well known. If 
the hand be placed against the wail, the contact differs from that which 
the tree sustains in a similar position, because between the latter there 
is always an interval of some centimeters through which the air cireu- 
lates freely. A white wall warms less than a black one, because it 
reflects readily the caloric which the latter absorbs. Also, the stratum 
of air lying nearest a white wall, receiving the same quantity of direct 
rays, in addition to the reflected ones, is found to be warmer than if the 
wall were black. It is precisely in this stratum of air lying nearest 
the wall that an espalier grows. Accordingly, the white color of a wall 
should increase the warmth which is received. by espaliers, while a black 
hue would tend to diminish it. 
*The Horticulturist. New York, 1860, vol. v, p. 134. 
tTransactions of the American Institute for 1864~65, p. 100. 
t The Prairie Farmer, Chicago, 1866, vol. xviii, p. 365. 
