3 4 



THE NURSERY-BOOK. 



of slats, usually 3-inch stuff. This shed screen is oftenest used 

 for the protection of tender plants, but it affords an exceedingly 

 useful and convenient place for the storage of pots and boxes of 

 slow-germinating seeds. 



Fig. 6. Shed Screen. 



Various frames and covers are employed for in-door seedage, 

 but they are designed to regulate atmospheric moisture and to 

 control temperature. They are more commonly employed in 

 the growing of cuttings, and are therefore described in Chap- 

 ter IV. 



Requirements of Temperature. Variations in temperature 

 exercise less influence upon seeds than variations in moisture. 

 Yet it is important that the extremes of temperature should not 

 be great, especially in small, delicate or weak seeds. Seeds will 

 endure greater extremes of temperature when dry than when 

 moist. This indicates that germinating seeds must be kept in a 

 comparatively uniform temperature. For this reason it is poor 

 practice to place seed-boxes in a window in full sunlight. Partial 

 or complete shade serves the double purpose of preventing too 

 great heat and too rapid evaporation. Various covered seed- 

 boxes are used for the purpose of maintaining approximately 

 the required temperature, but as they are oftener used in bud- 

 propagation, they are discussed in that connection. 



Bottom heat is helpful to germination in most seeds, but, except 

 in the case of certain tropical species, it should not be strong. 

 It is a common practice to place the seed-boxes on moderately 

 cool pipes under benches in a greenhouse. Seeds of hardy 

 annuals and perennials do not require bottom heat, although 



