H. D. Young 



99 



TABLE 4 



Data pertaining to carbohydrates in clcaned and uncleaned halves of dusty leaves. 



{See also Table 5) 



Date, 1910 



Total hexose-sugars 



Cleaned 



Nov. 

 8 



9 



10 



II 



14 



15 



16 



17 



21 



22 



28 



29 



30 



Dec 



2 



3 



4 



Average 



% 

 4-25 

 77 



69 

 63 

 49 



Ol 



12 

 36 

 29 

 97 

 99 

 34 

 43 



31 



48 



45 



Uncleaned 



% 

 329 

 3.78 

 3-80 

 550 

 5-13 

 4-75 

 5-48 

 5-86 



311 

 3-71 

 4.62 

 4.06 

 3-81 



2.92 



3-49 

 2.38 



Starch 



Cleaned 



Uncleaned 



% 

 3-23 

 2.83 

 1.03 

 1.02 



2.59 

 3-80 



5-27 

 5-36 



0.55 

 0.91 



I-I3 



I.IO 



IIS 



1.22 

 0.83 

 1.22 



% 

 3-68 



2.31 



I.Ol 



0.92 

 4.04 

 2.54 

 3-II 

 2.52 

 0.80 

 0.73 

 i-iS 

 1.63 

 2.16 



0.87 

 i.ii 

 I-3I 



Total carbohydrates 



Cleaned 



% 

 7-48 

 6.60 

 4.72 

 4-65 

 8.08 

 6.81 



9-39 

 10.72 



3-84 

 3-88 

 4.12 

 6.44 

 4-58 



453 

 331 

 4.67 



Uncleaned 



% 

 6.97 

 6.09 

 4.81 

 6.42 

 9.17 

 7.29 



8.59 

 8.38 



3-91 



4.44 



5-77 

 5-69 

 5-97 



3-79 

 4.60 



3-69 



3-78 



4.10 



2.07 



1.87 



5.85 



5.97 



quite close agreement. The cleaned half-leaf samples seem to con- 

 tain a little more starch and a little less sugar than the dusty samples, 

 the total carbohydrate being the same within the limit of error. 

 The difference between the relative amounts of starch and sugar 

 may possibly be accounted for by a greater activity of the diastase 

 of translocation in the less intense light in the shaded half of the leaf. 



Repetition of the TESTS. This work was repeated the follow- 

 ing year with two points in view : to determine whether the differ- 

 ences might not be greater at a more actively growing season ; and to 

 determine the relative activity of old and new leaves. On the orange 

 trees there are always leaves of various ages, from a fev^ days, pos- 

 sibly, to several years. A comparison of the activities of leaves a 

 few weeks old with those of a year old would seem to determine 

 whether any permanent injury to the leaf had taken place, since 

 the dust does not adhere to the surface of new leaves. 



The figures in Table 5 show a much greater formation of carbo- 

 hydrates than those in Table 4. In Table 5 the difference between 

 the cleaned and uncleaned samples, as regards starch and sugar, 

 has disappeared. 



