UPWARD TRANSPORT OF ORGANIC MATTER 31 



the ring, but, even though water was moving through the 

 xylem to the leaves above, there was insufficient sugar 

 carried through this tissue to cause any starch deposition 

 in the defoliated part, whereas when the phloem connection 

 to the leaves below was not interrupted by a ring, this 

 region was densely filled with starch. 



Similar results were obtained in the experiment cited on 

 page 50. In this instance, however, the ring at the base, R', 

 was omitted. In this series (Curtis, 1923, p. 376) not only 

 were starch tests made with iodine, but the dry weights and 

 volumes of the xylem were determined. These data, as 

 shown in Table 3, are in complete agreement with the 

 starch tests and show that the average dry weights of the 

 xylem of the defoliated regions in treatments 1 and 3 

 are greater than those of treatment 2 by 29.4 and 77.6 per 

 cent, respectively, and the dry weights per unit volume were 

 10.5 and 24.0 per cent greater. 



Experiments almost exactly like these have subsequently 

 been carried out by Mason and Maskell (19286, p. 582). 

 Their experimental material was the cotton plant, and 

 though in these experiments they do not give data on dry 

 weights or weight per unit volume, they do give data on 

 the sugar concentration of the sap of the bark and the 

 total carbohydrate contents of the bark and wood in the 

 defoliated region. These are of additional interest because 

 increases or decreases in carbohydrate contents are given 

 over 12-hr. periods. Curves showing such data are given 

 in Fig. 4. 



The evidence is clear therefore that, even when a move- 

 ment of water through the isolated region is insured, 

 carbohydrates are not carried into, and stored in, such a 

 region. Evidence cited in Sec. 5 also shows that if such a 

 region, isolated by double rings, is full of starch to begin 

 with, it is not emptied through the xylem, even when there 

 is active movement of a water stream through this region. 



The responses to ringing and double-ringing that have 

 been found to vary with the season of ringing are easily 

 explainable when one takes into consideration the amounts 



