164 MANUAL OF GARDENING 



A very good temporary protection may be given to tender 

 plants by using four panes of glass, as explained in Fig. 193, the 

 two inner panes being held together at the top by a block of 

 wood through which four nails are driven. Plants are more 

 likely to burn in these glass frames than in the hand-boxes, and 

 such frames are not so well adapted to the protection of plants 



in very early spring; but they are often 



useful for special purposes. 



In all forcing-hills, as in coldframes and 



hotbeds, it is exceedingly important that 



the plants receive plenty of air on bright 

 ,^^ ^, , . , .„ days. Plants that are kept too close be- 



193. Glass forcing-hill. -^ ^ u ^ ,, fi ^ ^ -t 



come weak or drawn, and lose the abihty 

 to withstand changes of weather when the protection is re- 

 moved. Even though the wind is cold and raw, the plants 

 inside the frames ordinarily will not suffer if the glass is 

 taken off when the sun is shining. 



Coldframes. 



A coldframe is nothing more than an enlarged hand-box; 

 that is, instead of protecting but a single plant or a single hill 

 with a single pane of glass, the frame is covered with sash, and 

 is large enough to accommodate many plants. 



There are three general purposes for which a coldframe is 

 used: For the starting of plants early in spring; for receiving 

 partially hardened plants that have been started earlier in 

 hotbeds and forcing-houses; for wintering young cabbages, 

 lettuce, and other hardy plants that are sown in the fall. 



Coldframes are ordinarily placed near the buildings, and the 

 plants are transplanted into the field when settled weather 

 comes. Sometimes, however, they are made directly in the 

 field where the plants are to remain, and the frames, and not 

 the plants, are removed. When used for this latter purpose, 

 the frames are made very cheap by running two rows of parallel 



