U6 



Principles of Plant Culture. 



flower-pots or large green leaves, as of the burdock, 

 are useful for- shading plants of the cabbage, tomato, 

 etc. 



In culture under glass, the glass is often thinly 

 washed with lime or clay to render it partially opaque, 



Fig. 63. Brush screen, tor shading tender plants In the open 

 ground. (After Bailey.) 



or lath screens are used either above or below the glass. 

 On greenhouse benches, sheets of thin paper or light 

 cloth screens are useful for shading cuttings, recently- 

 planted seedlings and germinating seeds. 



Shading should never be so put on as to prevent a 

 free circulation of air about the plants. 



A shade that obstructs only a part of the rays of sun- 

 light at a time, as does the lath or brush screen, is 

 generally preferable to one that continuously breaks 

 the force of all the rays, as does paper or whitewashed 

 glass. 



236. Cauliflower Heads should be Sheltered from 

 Sunlight to prevent the formation of chlorophyll in 

 their cells (59), which darkens their color and gives 



