40 
GREENHOUSE CONSTRUCTION AND HEATING. 
Bottom ventilators, or “louvres,” are occasionally fixed 
in the side-walls below the staging, whether there are any 
Kia. 24. 
glazed or other 
ventilators above— 
on the top of the 
wall—or not. In 
this way, air may 
be admitted with- 
out its acting 
directly the 
plants, and in cold 
weather dangerous 
draughts or chilly 
airare thusavoided. 
Houses for pelar- 
goniums, begonias, 
and other plants 
on 
that enjoy a free current of air through them may be 
advantageously constructed in this way, and for some 
descriptions of orchids 
this is also a very 
suitable method. If 
there are hot-water 
pipes beneath the 
staging, air admitted 
thus will be warmed 
before it reaches the 
plants, especially if 
there is another wall, 
ge A 
& 
FIG. 25. 
also fitted with openings, next the pathway, as shown in 
Fig. 24. 
