NOTES AND ABSTRACTS. 
483 
of starch by ordinary diastase and that of cane sugar by citric acid inversion 
were avoided also by new methods, of which full details are given. 
The (a) leaves and (b) stalks of mangolds were analysed for sugars at three 
different stages of their growth, samples being taken every two hours over a 
complete twenty-four hour period on August 26, September 10, and October 11. 
Starch and maltose were always absent. Saccharose and hexoses were always 
present. The ratio of hexoses to saccharose increases in passing from leaf to 
stalk, suggesting that it is cane sugar which is first formed in the chloroplasts 
of the leaf directly from the C0 2 of the air, and that it undergoes regular and 
increasing inversion as it passes downwards to the root. The inversion may 
be brought about by invertase on the surface of the sieve tubes. If it were 
possible to analyse the contents of the mesophyll tissue alone, excluding all the 
small veins which act as conducting channels to the midribs, the authors are of 
opinion that no reducing sugars would be found in that tissue. The conversion 
of saccharose into hexoses for purposes of translocation is necessary, as otherwise 
diffusion would be proceeding from a place of low to one of high concentration. 
Moreover, the work of various observers goes to show the probability that the 
protoplasm of the beet is impervious to cane sugar. The reconversion of the 
hexoses into saccharose in the root is not accounted for, but a special synthesizing 
mechanism is postulated, such as the " saccharogenic enzyme" of Barbet. 
/. E. W. E. H. 
Carbohydrates in Plants, Studies of the Formation and Translocation of. 
II. — The Dextrose-Laevulose Ratio in the Mangold. By William A. Davis 
(Jour. Agr. Sci. vol. vii. pt. iii. pp. 327-351, Feb. 1916 ; figs.). — The polarimetric 
determination of the dextrose-laevulose ratio in extracts of plant tissue is 
vitiated by the presence of optically active substances, such as amino-acids and 
amides, which are not completely removed by the basic lead acetate (or other 
substance) used to clear the solution. Hence differences of results are obtained 
for saccharose determinations in the mangold by polarimetric and reduction 
methods respectively. The results are also affected by the reducing power 
and rotation of the pentoses (arabinose, xylose, and d-ribose) which may be 
present in the alcoholic extract [see preceding abstract]. Until more reliable 
results can be obtained for the true dextrose and laevulose contents, independent 
of polarimeter data, it seems justifiable to assume that the two sugars travel 
in nearly if not exactly equal proportions to the root, where re-transformation 
takes place.—/. E. W. E. H. 
Carbohydrates in Plants, Studies of the Formation and Translocation of. 
III. — The Carbohydrates of the Leaf and Leaf-stalks of the Potato. The Mechanism 
of the Degradation of Starch in the Leaf. By William A. Davis and George 
Conworth Sawyer (Jour. Agr. Sci. vol. vii. pt. iii. pp. 353-384 ; figs.). — The 
potato, unlike the mangold, forms considerable quantities of starch in its leaf. 
The object of the investigation was to ascertain whether, assuming that the 
starch is removed from the leaf after being broken down to maltose by diastase, 
maltose is correspondingly an intermediate stage in the synthesis. It was 
ascertained that maltose is entirely absent from the leaf and leaf-stalks of the 
potato both by day and by night. This striking result led the authors to review 
Brown and Morris's work of 1 893 . The latter experimenters found considerable 
quantities of maltose in the Tropaeolum leaf. The present authors show, however, 
that the presence of maltose was a result of Brown and Morris's method of analysis, 
which included the preliminary drying of the material in an oven. In such 
circumstances the enzymes present in the tissue would ultimately be destroyed, 
but not simultaneously. The most sensitive to heat and therefore the first to 
disappear would be maltase. A temperature above the point at which maltase 
is destroyed would be an optimum for the action of diastase, which would there- 
fore break down starch to maltose, but the latter would remain as such in the 
absence of maltase, and thus would account for Brown and Morris's results. 
The authors hold that the removal of starch from the leaves at night is effected 
by more than one enzyme, that the degradation does not stop, as Brown and 
Morris supposed, at maltose but at dextrose. They cite other considerations 
tending to show that plant tissue cannot utilize either starch, or maltose, or 
saccharose, but must first break them down to simple hexoses. 
The remainder of the paper is occupied with a discussion of the experimental 
results of the analysis of the leaves and stalks of the potato. The experimental 
methods adopted were the same as those in the case of the mangold experiments. 
The general results, moreover, were similar, for, in the case of the potato, saccharose 
is greatly in excess of the hexoses in the leaf and greatly in defect of them in the 
stalk. 
