342 The Dextrosc-Laevnlose Ratio in the ManyoUl 



A between the values found for saccharose by reduction and polarisation 

 is greatest, the polaiisation figures being 20 to 30 per cent. high. 



During the greater part of the day (except at 9 a.m., when j = 1'45) 



the proportions of apparent dextrose and laevulose are very nearly 

 equal, as might be expected if they were formed from saccharose, but 

 at night the dextrose appears to be in excess. A striking difference 

 from Series II is that the dextrose instead of rising during the day and 

 then falling, at first appears to fall and then to rise (see Fig. 3) ; at night, 

 instead of a rise and fall, there is a fall between 9 and 11 p.m., followed 

 by a gradual rise to 5 a.m. But in both series there appears to be a 

 similar periodic character in so far as there are three rises and three 

 falls in the 24 hours. In Series III the variation of the apparent dextrose 

 is most striking as taking place along practically straight lines in a very 

 regular manner. The apparent laevulose curve in Series 111 is entirely 

 different from the dextrose curve but it follows fairly closely the curve 

 of total hexoses, and less closely the curve of saccharose. The fluctu- 

 ations of the apparent laevulose are considerably greater and more 

 abrupt than tho.se of the dextrose, as was also the case in Series II. 



The curve showing the variation of j^ is also given. falls from 



9 a.m. to 1 p.m., then rises slowly and more or less by successive steps 

 to a maximum at 11 p.m., when it again falls and rises twice before 

 9 a.m. 



B. Stalks and Mid-ribs. 



The most striking fact which appears from the data given in Tables 

 IV to VII is that in the stalks and mid-ribs the apparent dextrose is 

 always in large excess of the laevulose. Whereas in the leaf the ratio 



Y does not depart much from unity*, in the mid-ribs and stalks it is 



rare to find this ratio anywhere in the neighbourhood of 1. Only in 

 the earliest stages of growth (August 26th) and then only in the top 

 half of the stalks, nearest the leaf, at noon and j^.m., when freshly 

 formed sugars from the leaf are passing into the stalks, does the ratio 



* The departure of this ratio from unity in Series I, Table I, is to bo attributed to 

 the impossibility, owing to the presence of optically active impurities, of ascertaining the 

 true proportions of dextrose and laevulose in these cases, where the reducing sugars are 



present in small amounts. In Series II and III, the ratio is nearly unity throughout 

 the whole 24 hours. 



