How to Grow Plants from Seeds 185 
the sash at the height desired. If the weather suddenly 
becomes cold or cloudy, the sash should be shut down. 
In extremely cold weather, and especially at night, 
the sash may be covered with straw, blankets, old carpet, 
or the matting which is made for this use. As spring 
advances, the sash may be raised higher and for longer 
periods during the day, until finally they may be re- 
moved, to be replaced only on cool nights. 
At the time seedlings burst from the soil they may be 
somewhat “ burned ” by midday sunshine. This may be 
prevented by spreading a single sheet of newspaper over 
them during the middle of the day for a day or two. 
.. Freshly transplanted seedlings should thus be shaded. 
Plants standing in the middle of the frame will receive 
more light than those at the edge; so it is a good plan 
to shift and turn the flats from time to time. Usually 
the growing plants are given all the sunlight that is 
available. 
After it is properly started, only a few minutes are 
required each day to care for the hotbed; but daily 
attention and management, according to changing 
weather, is absolutely necessary for the best results. 
Construction and use of a cold frame. A cold frame 
consists of a frame with a sash or cloth covering. It is 
usually placed directly on the ground. No artificial heat 
is supplied as in the hotbed, but the frame affords pro- 
tection from the cold air of the outside. The covering of 
sash or cloth helps to retain over night the heat received 
from the sun during the day. 
Cold frames are especially useful for hardening seed- 
lings previously grown in a hotbed. This is done by 
