W. A. Davis, A. J. Daisii and G. C. Sawyer :301 



of the movement in the stalks; thus in Series II, when the sugars are 

 rapidly increasing in the leaf in the morning, the total sugars in the 

 mid-rib have a higher value (29-95 per cent, at 10 a.m.) than in the 

 slalks (25-32 per cent.), the proportion of sugars to total alcohol-soluble 

 matter being much higher also (49-2 per cent, as compared with 38-7 

 per cent.). But by 4 p.m. a large proportion of the sugars which were 

 in the mid-rib in the morning have passed into the stalk, so that the 

 numbers are now reversed (28-68 per cent, in mid-ribs, 31-56 per cent, 

 in stalks for the sugars; 45-7 and 47-2 per cent, for the proportion of 

 sugars to total alcohol- soluble substances). At 11 p.m. stalks and 

 mid-ribs are practically identical ; at 4 a.m. the large accumulation of 

 sugars in the leaf at 2 a.m. is already passing out of the mid-rib and is 

 accumulating in the stalk, thus increasing the proportion of sugars 

 therein, this being shown by the three successive values for total sugars 

 in the stalks, 27-58, 28-97 and 31-76 at 11 p.m., 4 a.m. and 6 a.m. By 

 10 a.m. a large proportion of the sugar conveyed to the stalk has 

 passed on to the root, so that the proportion of sugars falls to its 

 minimum at about this hour. 



The problem of translocation is complicated by the fact that several 

 operations are actually occurring simultaneously and the actual analy- 

 tical data only give the net results of all these ; thus sugars are, during 

 the daytime, being formed in the leaves, but at the same time are 

 passing/rom the leaves into the mid-ribs and stalks; it has been shown 

 above that the top and bottom halves of the stalks have very different 

 compositions and the relationship between the sugars in the mid-ribs 

 and stalks and the top and bottom halves of these stalks is again 

 complicated by the fact that the roots are continuously receiving the 

 sugars from the lower part of the stalks, and the tops of the stalks 

 from the mid-ribs. It is interesting in this connection to compare the 

 curves for the total hexoses in the stalks in Series II with those for the 

 mid-ribs in the same series, Figs. 9 and 10. Whereas in the daytime 

 the hexose in the stalks first increases, keeping pace with the increased 

 formation in the leaf, and then falls, in the mid-ribs the hexose falls 

 continuously throughout the day and night till about 4 a.m. It thus 

 appears that the removal of the sugars from the mid-ribs to the stalks 

 during the day takes place somewhat faster than the sugars pass into 

 the ribs from the leaf tissue. It is seen too that the saccharose content 

 increases somewhat in the mid-ribs during the night, whereas in the 

 stalks it remains practically constant. Both facts are probably due to 

 a common cause, which comes out more clearly from later considera- 

 tions, that the sugar has to pass from the mesophyll into the veins and 



