STEVENS] 



THE SAP CURRENT: AN EXPERIMENT 



97 



ceedingly receptive for a true conception of the facts. The experi- 

 ment is readily made with pupils or people of any age anywhere. It 

 is particularly striking in the spring time, although it is convincing at 

 any time when there is foliage on the branches. 



The accompanying illustration shows the steps of the experiment as 

 conducted by one of my classes this year. The rose twig shown in Fig- 

 ure i has been girdled, that is, the bark has been removed, leaving the 

 sap-wood bare. The length of the girdled belt is immaterial, -)4 to 

 2<£ of an inch is very good. Figure 2 shows the twig after girdling and 



FIG. I FIG. 2 FIG. J 



Fig. 1 is a photograph of a girdled rose branch. In Fig. 2 the girdle is covered with wax. In Fig* 

 3 the stem is thickened (see the arrow) above the girdling, five weeks after girdling. 



the wounds covered with grafting wax to prevent the sap-wood from 

 drying up, and insects and fungi from interfering. Figure 3 shows a 

 girdled and waxed twig five weeks after the twig had been girdled. 

 The waxed and girdled place is to be noted on the lower part of the 

 stem ; the large mass of thrifty, healthy, unwilted foliage is seen above 

 the girdled part. This experiment was particularly striking since the 

 girdling was done soon after the buds were opened in the spring, that 

 is, when the leaves were opening fastest, and the required supply of 

 sap was consequently very great. The twig evidently (see Fig. 3) 

 was not wilted, nor would it wilt in months or even years. 



