GENERAL REMARKS ON HEATING. 143 
degrees—if not of too long continuance, and especially if 
the structure occupies a moderately sheltered situation, 
but when the thermometer falls below about 25 degrees 
Fahr., or if even a less degree of cold is maintained for 
more than a few hours, the low temperature will gradually 
penetrate to the interior, and soon leave its mark on any 
plants of a tender or delicate description. Plants standing 
near the glass are naturally affected first, and it is a well- 
known fact that the tissues of such as are in a comparatively 
moist condition at the time, or have been grown rapidly in 
rich soil with plenty of water, are decidedly more tender or 
“soft,” and therefore liable to injury from frost, than those 
of others that have been to some extent starved or kept on a 
short allowance of moisture and nutriment for some time 
previously. Thus common ‘‘geraniums” (zonal pelar- 
goniums) may be rendered practically hardy, and be safely 
preserved through an ordinary winter in a totally unheated 
structure, simply by affording them no water whatever, from 
the middle or end of November—or whenever the cold 
weather sets in—until some time in March, when the spring 
returns. Under this treatment the plants lose nearly all 
their leaves, and become mere ‘“‘bare poles,” but they will 
not perish, and when subjected to the influence of warmth 
and moisture again in the spring, quickly burst into luxuriant 
growth and blossom again, 
Much may also be done towards preserving more or 
less tender plants through the winter in unheated houses 
or pits by covering the glass with some non-conducting 
material in frosty weather, and also by plunging the pots 
in ashes, cocoa-nut fibre refuse, or the like—but this will 
be more fully dealt with presently. 
