1868. ] 
ON THE WATERING OF OUT-DOOR PLANTS. 
157 
chance of frost, the morning is the only time when water can he given to 
out-door plants with safety; but during summer, when injury from an 
excess of cold is impossible, the case is wholly altered. 
I agree with Mr. McBey that the two acknowledged agents in promoting 
vigorous growth are Heat and Moisture; but if his paper is carefully read 
it will be observed that its purport is almost wholly directed to the preven¬ 
tion of any loss of heat. He is not as careful to husband the water, as he 
is to preserve caloric. Now, the object in applying water to plants is that 
they may be able to use it. This is well nigh impossible when it is applied 
to them on the morning of a bright summer day. Prompt as is the action 
of vegetable life, a thirsty sunbeam is more than a match in speed for a 
thirsty root or a parched leaf. While these drink up their grains of mois¬ 
ture, the sun has borne away gallons of the water that has just been applied. 
This, then, is my first objection to morning watering. It causes a loss of, 
probably, 80 per cent, of the water applied. My second is, that this loss 
or evaporation takes place at the wrong time, and in the wrong way. The 
cooling effects of day-evaporation are more injurious to plants than the 
same effects at night—excepting, always, it is carried to excess at the latter 
period, and this the average temperature of our summer climate prevents. 
Hay-evaporation is more rapid than night, and therefore a greater amount 
of cold is actually produced on the evaporating surface during the day than 
at night; for the cold bears a constant ratio to the rapidity of the evapo¬ 
ration, and it is more than doubtful whether the presence of the sun can 
compensate the plants for the great and sudden loss of heat sustained by 
day-evaporation. This loss is also sustained at the worst possible time. 
Just when the light and heat of the sun are arousing and quickening the 
slumbering activities of plant life to the utmost, splash comes a deluge of 
water, and that caloric that was designed to nourish growth is instantly 
diverted to another purpose—that of the lifting-up and rapid removal of 
the moisture. Thus there is not simply a loss of most of the water, but a 
cold chill is given at the time when the warmth was most needed; and 
from the mere fact that the powers of life seem most active during the day, 
there can be no question that a day chill is much more injurious than a 
night one. Hence the burning of wet foliage during bright sunshine is not 
only identical in its results to a pinch of frost, but may absolutely be 
the same thing, and arise from an excess of cold originating in the unna¬ 
tural activity of evaporation. Absolutely as much or more heat may be 
lost to the plant by morning as by evening watering. 
Morning watering has this additional drawback, that it sends away the 
heat at the wrong time, and the water also before it can possibly be drunk 
up by the plants. Now, as the object of giving the water was that the 
plants might use it, it seems reasonable, to say the least of it, that it should 
