The Greenhouse and Frame 
213 
In a greenhouse, plants are under perfect control, but 
the regulation of the temperature must be well understood; 
how to admit the necessary supply of fresh air, and how 
to apply water to the roots of the plants; also when to 
supply or withhold moisture from the atmosphere. 
The heat must be regulated according to the class of 
plants grown in the house. If their native country is 
Section of Greenhouse 
warm, then the house will have to be warm also; but if 
their native country is cool, the house must be kept cool 
for their successful cultivation. All plants, those from 
warm countries as well as those from cool ones, require 
fresh air, and it is a most difficult matter to supply this, 
especially during our severe winter season. On no account 
must there be draughts in the plant houses; plants are 
living things, and suffer very readily if exposed to draughts. 
Everyone knows that chills and colds are contracted as the 
effect of sitting in a draughty place. Though we cannot, 
