164 THE PRINCIPLES OF FLORICULTURE 



cell development be more rapid at the base of the cutting 

 than at the tip. Development of the growing-point should, 

 therefore, be retarded until root-formation has occurred. 

 Because of this, a soil temperature several degrees higher 

 than the atmospheric temperature is essential. 



Soil moisture. While cuttings without roots have no 

 means of taking in moisture, it is essential that they be 

 placed in a moist medium so that cell growth may go on 

 rapidly. The soil water should be uniform and there 

 should be sufficient drainage so that it will be constantly 

 changed that aeration may occur. 



Atmospheric temperature and moisture. A hot, dry 

 atmosphere increases the rapidity of transpiration from the 

 leaf surface and a cool moisture reduces it. As the cutting 

 has no roots through which to take in moisture, and as it 

 has no power of taking it from the air through the leaf, 

 every effort should be made to retard the transpiration. 

 A cool, fairly moist atmosphere should, therefore, be 

 maintained in the cutting-bench. 



Diminished light. Under strong sunlight the physio- 

 logical process in the manufacture of plant food goes on 

 rapidly. When sufficient crude material is available from 

 which to manufacture food, growth is rapid and the vigor 

 of the plantlet is shown by its deep, green color. If there 

 is a diminished supply of crude material, the chlorophyll 

 bodies in the plant cell are broken down in strong sunlight, 

 and a yellow, sickly appearance is consequently given the 

 cutting. Strong sunlight also increases the temperature 

 in houses ; therefore, cuttings thrive better in partly di- 

 minished light. The amount of light required by different 

 species during the rooting process varies. At no time 

 should the cutting be allowed to spindle because of de- 

 ficient light ; on the other hand, the cutting should never 



