286 The Carbohydrates of the Maiujold Leaf 



and, after the attempted conversion of the starch with taka-diastase, is 

 precijjitated as a seiiii-crystallinc mass by basic lead acetate. Whether 

 this substance can give rise directly to cane sugar or reducing sugars 

 on liydiolysis can only be decided by a special investigation, but it 

 would appear that this or some kindred substance is the source of the 

 great increase of sugars which occurs between midnight and 3 a.m., 

 both in the September and October pickings. 



As compared with the earlier picking in August the following are 

 the outstanding features: 



1. The proportions and range of variation of the sugars are con- 

 siderably greater: 



On August 26th-27th, the saccharose varied from 3-05 to 1-5 per 

 cent., hexoses from 2-15 to 0-2 per cent. 



On September lOth-llth the saccharose varied from 8-27 to 4-24 per 

 cent., hexoses from 8-9 to 5-4 per cent. 



This, too, in spite of the fact that September 10th was a dull, cool 

 day unfavourable to photo-synthesis. 



2. The relative position of the saccharose and hexose curves has 



changed ; whereas in August the cane sugar curve was always above 



I s 

 the hexose curve, the ratio -^" varying between the limits 0-13 and 0-71, 



u.s* 



in no case reaching l-O, on September lOth-llth the hexose curve is 



throughout the 24 hours above the cane sugar curve, except for a moment 



at 2 a.m., when the two sugars are present in nearly eijual amounts. 



i.s. 

 During the 24 hours the -^^ varies from ()-!)4 to l-Go. 



3. During the later period of the night, when the proportion of 

 sugars is falling, the leaves became nothing like so depleted of sugars 

 as in the earlier stage of growth; whereas on August 26th-27th the 

 cane sugar fell to 1-5 per cent, and the hexoses practically disappeared, 

 on September lOth-llth the lowest value reached by the cane sugar 

 was 4-24 per cent, and by the hexoses 5-4 per cent. 



Pentosans, Mailer Insoluble in Ahohol and Pentoses. 



As at the August picking, but in a far more unmistakable manner, 

 the curve showing the proportion of leaf substance which is insoluble 

 in alcohol runs exdclli/ ptiniUi-l to the penlosfin curve (see Fig. 5). It is 

 a striking fact that from 10 a.m. to 1 p.m.. in spite of the large increase 

 in the sugars, that is of Tuatter sohdile in alcohol, there is a large actual 

 increase of substances which arc insoluble in alcohol, and exactly 



