GROWING EARLY VEGETABLE PLANTS UNDER GLASS 153 



bility, and the flats are not uniform in size. Because of 

 varying dimensions they cannot be placed in the frames 

 without loss of space. When this annual loss is taken 

 into account, it makes a strong argument for a uniform 

 size of flats. When new lumber is used, the flats should 

 be made to fit in the frames or on the greenhouse bench 

 without loss of space. Chestnut is a durable wood for 

 this purpose. The sides and bottoms should be made of 

 and the ends of ^4-inch pieces. When nailing on 



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FIG. 40. RYE-STRAW MAT 



the bottom pieces, about J^-inch cracks should be left 

 between them, to provide good drainage. Two inches is 

 ample depth for most purposes. A deeper flat requires 

 more soil and makes handling heavier. If the flats are 

 about 2,]/2 x 16 x 22*/2 inches, outside dimensions, three 

 of them will fit in a 6-foot frame without an appreciable 

 loss of space. Flats of smaller size are convenient for the 

 retail plant business. 



