Carbon A ssimilation. 
221 
II. Stage of intermediate growth. 10 a.m., September 10— 
8 a.m., September 11, 1912. 
III. Final stage of growth. 9 a.m., October 11—7 a.m., 
October 19, 1912. 
In each case, the leaves and leaf stalks were treated separately. 
In the first series the upper and lower parts of the leaf stalk were 
dealt with separately ; in the second series, the midribs of the leaves 
were subjected to a separate analysis ; in the third stage of growth 
the midribs and leaf stalks were treated together. Their results 
are all calculated in terms of the total vacuum dried matter of the 
leaf. 
It may be mentioned at once that Davis and his collaborators 
found starch was absent from the leaves and petioles of the mangold 
at all stages of growth except the very earliest. Similarly, no maltose 
was ever found in either leaves or petioles of this plant at any time. 
The quantities of other carbohydrates present in the leaf are 
indicated in the accompanying figures, which are based on the 
numbers and curves given in Davis, Daish and Sawyer’s paper. 
Fig. 14 shows the variation in content of the sugars of the 
mangold leaf found during 24 hours on August 26-27, 1913. The 
most noteworthy features of these results are:— 
1. Both hexoses and sucrose increase rapidly in quantity 
after daybreak and reach a maximum about mid-day, after which 
the quantity present falls off fairly regularly and rapidly until the 
following dawn. Practically the whole of the hexose sugar disappears 
and about half the sucrose. These changes are closely parallel to 
the temperature curve (and probably also to the curve of light 
intensity). 
2. The quantity of sucrose is always greater than that of 
hexose. 
3. The variations in the quantity of cane sugar are small, the 
4. The quantity of pentosan remains practically constant 
limits between being 3'11% and l‘5%, whereas the hexoses vary 
between 0-77% and 2' 16%. 
throughout the day, the fluctuations being probably within the 
range of experimental error. The same holds for the matter 
insoluble in alcohol. Davis and his co-workers consider the 
increase they found in the values of these substances to be really 
significant, but if this were so, there should be either a sudden fall 
in these values at sunrise, or the proportion of them in the leaf 
should go on increasing from day to day. As a matter of fact, in 
