GROWING EARLY VEGETABLE PLANTS UNDER GLASS 1 59 
off the mats by taking hold of the lapped-over ends. If 
wet, they should he spread flat on the ground or, better 
still, supported on a fence to facilitate drying. To cover 
the frames in the evening when the mats are wet, proceed 
as follows : Walk on the mat, reach backward, grasp the 
far end with both hands, walk over the frame at a cross- 
bar and drop the mat in place. When dry, they are 
handled rapidly and with ease. 
Mats are also useful in shading plants. The glass may 
be covered entirely in hot weather, or the opposite edges 
of the mat may be turned back, exposing 6 to 12 inches 
of glass along each side of the frame. This method of 
shading is especially valuable when transplanting is done 
late in the spring. 
219. Hardening plants. — This process is the firming of 
the tissues in order that the plants will be able to endure 
the hardships of transplanting and of open-ground condi- 
tions such as freezing, hard drying winds or hot sunshine, 
any of which may damage or destroy soft, tender plants. 
Figure 42 shows a frame of well-hardened cabbage plants 
which when photographed were of reddish-blue color, 
short and stocky. Such plants will stand a tempera- 
ture of 12 or 15 degrees above zero. 
Plants are hardened by watering sparingly, subjecting 
them to low temperatures and by providing free ventila- 
tion. These operations are equally valuable. When 
hardening is begun, no more water should be used than 
is necessary to prevent serious wilting. Air is admitted 
more freely from day to day. At the end of three or four 
days the sash may be removed entirely during the day, 
and the frames closed late in the evening and opened ear- 
lier than usual the next morning. Matting is not prac- 
ticed after a few days more of such treatment and, finally, 
no protection of any kind is given day or night. This 
general plan of hardening is primarily for the more hardy 
plants, as cabbage and lettuce. Tomatoes, peppers and 
