r J 



with -grafting-wax as before. If it is desired to maintain 

 the soil atmosphere unchanged during this operation a slow 

 stream of the proper gas can be kept flowing through the 

 pot and outward past the stem while the seal is being 

 reconstructed. 



In very hot weather the grafting-wax may become 

 so soft that it leaks downward by gravity or blows out 

 under slight internal pressure. This can be prevented 

 by using a grafting-wax of higher melting point (that 

 is, one containing more rosin), by making narrower the 

 annular space between the sealing-wax collar and the 

 stem, or by packing cotton, later saturated with melted 

 grafting-wax, very tightly into the lower third of the 

 annular space between collar and stem. Hone of these 

 expedients is fully satisfactory and it is better not 

 to attempt experiments in very hot weather. The unmodi- 

 fied technique has been used successfully with green- 

 house temperatures up to 35° C. (y5° £*•)• At such high 

 temperatures it is well to shade the seal from the sun 

 by means of a paper collar, a covering tuft of cotton, 

 or some similar device. 



The three porous clay cups of the auto-irri- 

 gator system are arranged in the soil at the apices of 

 a triangle at the center of which is the plant. The 

 connections between the cups and to the water reser- 

 voir are shown in figjtre 3, the three cups being here 

 shown in line, instead of in the triangular arrangement 



