274 
OPERATIONS FOR JANUARY. 
did not mislead, in the instance before us, a feeling has prevailed in favour of the 
literal acceptation of the term, which has led to the most erroneous practices. It 
is therefore necessary to say that shelter consists rather in the retention of the 
natural heat of the plant, and of the atmosphere that surrounds it. 
Often as we have impressed the above consideration on the public mind, we 
cannot refrain from here stating that the legitimate deduction from such premises 
is, that the means and material of protection should be external^ and between it& 
object and the cold air ; extending the advantages of this provision, when requisite, 
(and only then,) by the introduction of additional heat from below. 
In greenhouses and pits which are properly covered by mats, straw-hurdles, or 
thatch, a fire will very rarely be needful to maintain a temperature above freezing. 
But there is another enemy to tender vegetation besides frost, and one, perhaps, 
more dangerous on account of its being little thought of. We mean excessive damp- 
ness. And where the air without is so humid or so cold that ventilation would be of 
no service, or cannot be afforded, fire-heat must be sparingly applied. The moisture 
we have yet spoken of, however, is that arising from natural causes ; but when 
plants have been newly watered, tliere are unavoidable exhalations which fill the 
air with humidity ; and if these cannot be discharged by the admission of a dry 
outer current, they should be dissipated by artificial heat. Still, never more than 
enough to effect the object ought to be employed, and it should cease with the 
accomplishment of the end for which it was intended. 
Stoves, again, may require a little higher temperature than greenhouses ; but if 
the plants have been judiciously managed, they will never be hurt by the thermo- 
meter ranging at 45^ and upwards, which heat may be mostly maintained by 
exterior shelter, aided occasionally by slight fires. Many degrees above this, in 
severe weather, will be injurious rather than beneficial, save for growing plants, or 
for those which it may be desirable to force. Especially should water be cautiously 
given at the present period, as it not only induces mouldiness, (than which nothing 
can be more unsightly or hurtful,) but occasions an unseasonable development, 
which alike weakens and endangers the plants. 
For delicate plants in the open ground, next to surrounding them, at some 
distance from the branches, with mats or tarred canvas, the most effectual method 
of preservation is to place two or three inches of any dry non-conducting substance 
over the earth around their stems. By this means, their roots are kept compara- 
tively warm, and are enabled to send a genial current into the branches, by which 
they are much assisted in maintaining their heat. Besides, most plants that have 
their branches destroyed will, if the roots and lower parts of the stems be kept 
alive, sprout forth with renewed vigour in the ensuing spring. 
