W. A. Davis, A. J. Daish and CI. C. Sawyer 298 



insoluble in alcohol, at the September picking (Series II) ; it would 

 probably have been the same also for the saccharose had not the day 

 been abnormally dull and cloudy, so that the range of temperature 

 was exceedingly small (A = 7°) and the increase of cane sugar (which 

 follows the temperature curve) correspondingly small (see Fig. 5). 



2. The proportion of pentosan appears to fall shghtly from the 

 first to the second Series, but then increases from the second to the 

 third. The apparent fall is really a relative effect, due to the large 

 increase in sugars and other soluble substances which are formed between 

 the dates of the first and second pickings. If the pentosans are calcu- 

 lated as percentages of the vacuum-dried leaf matter which is insoluble 

 in alcohol, we get a steady increase in the amount of pentosan constituent 

 as the season advances, as follows : 



Series I. Pentosans form 8-58-9-61 per cent, of the insoluble leaf 

 matter. 



Series II. Pentosans form 9-83-10-85 per cent, of the insoluble 

 leaf matter. 



Series III. Pentosans form 13-70-15-35 per cent, of the insoluble 

 leaf matter. 



In passing from Series II to Series III, a very large increase in the 

 proportion of pentosan constituents occurs, pointing probably to an 

 increase in lignification during the interval. 



3. The hexoses more and more predominate in the leaf as the 

 season advances; at first they form only a fraction of the saccharose 



^-^ varies from 0-13 to 0-71 in Series I ), but later on they become equal 

 c.s. / 



