284 The Carholujdratvx of the Maugoltl Leaf 



prevailed; the rise of temperature (50-53°) was slight from 10 a.m. to 



1 p.m., when the maximum was reached, and the correspondini; increase 

 in saccharose was very small, viz. from i-5I to 1-62 per cent. On tlie 

 other hand the increase of he.xoses takes place far more rapidlv, as was 

 the case in August, but with this exception, the geiteral sluipe of the 

 hexose curve is the same as that of the saccharose curve. In both 

 cases, two peculiar maxima appear (at G p.m. and 2 a.m.) which were 

 not found at the earlier stage of growth, but reappear, as we shall see 

 later (see Fig. 6), in October. Both the cane sugar and reducing sugar 

 after reaching a maximum at about 2 p.m., corresponding with the 

 temperature maximum, begin to fall off slightly up to 4 p.m., when a 

 sudden rise in both sugars occurs, just before sunset, maxima A and A' 

 being reached which are considerably higher (about 50 per cent.) than 

 the highest values previously reached. Similar maxima are found in 

 the October picking (Fig. 6) just after sunset. These sudden increases 

 in the sugars at this time of day find a parallel in the potato leaf (see 

 p. 366, and Fig. 1) in an equally sudden increase in the starch (from 



2 to 6 per cent.). It may be that the rise in the sugars may be accounted 

 for by a cessation in their translocation from the leaf, leading to an 

 accumulation in the leaf tissue. But from 6 p.m. to 8 p.m. both sugars 

 are again falling; at 8 p.m. a second rise sets in, which is more rapid 

 in the case of the saccharose than of the hexoses, the maximum B 

 for cane sugar being actually higher than that for the reducing sugars, 

 B' . At this point the percentages of saccharose and hexoses are nearly 

 the same, viz., about 8 per cent. ; the percentage of cane sugar at this 

 point is far higher than at any previous hour of the day, being nearly 

 double that corresponding with the maximum reached at 2 p.m. when 

 the leaves were exposed to direct light, and \\ times the value reached 

 at 6 p.m. Just as the night rise of saccharose was more rapid than that 

 of the hexoses, the falling off of the cane sugar is also more abrupt. 

 It is noteworthy that the increase of hexoses from 8 p.m. to 2 a.m. and 

 the subsequent decrease from 2 a.m. to 8 a.m. take place along exactly 

 straight lines; with the cane sugar this is not strictly the case. The 

 fall of hexose continues also some little time after sunrise, but the sac- 

 charose apparently responds at once to the daylight and increases in 

 amount. 



It is a very striking fact that although the curves for saccharose and 



the hexoses are of so complicated a character, the curve showing the 



i.s 

 variation of the ratio -^^ (that is invert sugar to cane sugar) is relatively 



