JOST, L., trans. by GIBSON, R. J. H.--"Plant Physiology," 564 pages, 172
figs., Oxford, 1907.

MARCHLEWSKI, L.--"Die Chemie des Chlorophylls," 187 pages, 5 figs., 7
plates, Berlin, 1909.

PARKIN, JOHN.--"The Carbohydrates of the Foliage Leaf of the Snowdrop
(_Galanthus nivalis L._) and their Bearing on the First Sugar of
Photosynthesis," in _Biochemical Journal_, Vol. 6, pages 1 to 47, 1912.

PFEFFER, W., trans. by EWART, A. J.--"Physiology of Plants." Vol. I, 632
pages, 70 figs., Oxford, 1900.

CHAPTER IV

CARBOHYDRATES

These substances comprise an exceedingly important group of compounds, the
members of which constitute the major proportion of the dry matter of
plants. The name "carbohydrate" indicates the fact that these compounds
contain only carbon, hydrogen, and oxygen, the last two elements usually
being present in the same proportions as in water. As a rule, natural
carbohydrates contain six, or some multiple of six, carbon atoms and the
same number of oxygen atoms less one for each additional group of six
carbons above the first one; e.g., C_{6}H_{12}O_{6}, C_{12}H_{22}O_{11},
C_{18}H_{32}O_{16}, etc.

Carbohydrates are classed as open-chain compounds, that is, they may be
regarded as derivatives of the aliphatic hydrocarbons. From the standpoint
of the characteristic groups which they contain, they are
aldehyde-alcohols. In common with many other polyatomic open-chain
alcohols, they generally possess a characteristic sweet, or mildly
sweetish, taste. In the case of the more complex and less soluble forms,
this sweetish taste is scarcely noticeable and these compounds are commonly
called the "starches," as contrasted with the more soluble and sweeter
forms, known as "sugars."

The characteristic ending _ose_ is added to the names of the members of
this group. As systematic names, the Latin numeral indicating the number of
carbon atoms in the molecule is combined with this ending; e.g.,
C_{5}H_{10}O_{5}, pentose, C_{6}H_{12}O_{6}, hexose, etc.

In recent years, as a matter of scientific interest, many sugarlike
substances which contain from two to nine carbon atoms combined with the
proper number of hydrogen and oxygen atoms to be equivalent to the same
number of molecules of water in each case, have been artificially prepared
in the laboratory and designated as dioses, trioses, tetroses, pentoses,
hexoses, heptoses, octoses, and