GRAFTING 95 



contact of scion and stock. The second point of 

 value consists in allowing the actinic ray in the sun- 

 light to act upon the chlorophyl in bud and bark of 

 the scion and it does not attract the destructive heat 

 ray. This is due to the translucency of the paraffin. 

 Certain embryonic cells become changed into cells 

 with different functions in the course of growth of 

 a plant. Some of these cells are grouped under one 

 class of what we call chromatophores in parts of the 

 plant which are exposed to the light. The chroma- 

 tophores commonly develop into chlorophyl bodies 

 or chloroplasts and the translucent paraffin allows 

 light energy to set them at work. Chemical life proc- 

 esses of the plant depend upon the activity of the 

 chlorophyl to such a degree that the translucency of 

 the protective covering for the scion in the new 

 grafting method seems to be important. Third, the 

 paraffin coating, impervious to air, maintains sap 

 tension equally in the course of fluctuation between 

 negative and positive pressures occurring between 

 night and day under varying conditions of light and 

 temperature. This maintenance of equalized sap 

 tension I believe to be important. Fourth, the par- 

 affin is waterproof and prevents evaporation from 

 the scion, which is otherwise prone to dry out be- 

 fore granulation of the wound has taken place in the 

 hickory or in other species which callus slowly. 

 Fifth, under a paraffin coating of stock and scion 

 the plant apparently does not have that impulse which 

 might otherwise lead it to introduce the protective 

 feature of what is called suberization, the spreading 



