icin
or populin, is found. This may be considered as the first appearance
of a real glucoside, if tannin be excluded from the list.

The oak, walnut, beech, alder, and birch contain tannin in large
quantities; in the case of the oak, ten to twelve per cent. Oak galls
yield as much as seventy per cent.[24]

The numerous genera of pine and fir trees are remarkable for ethereal
oil, resin, and camphor.

The plane[25] trees contain caoutchouc and gum; peppers,[26] ethereal
oils, alkaloids, piperin, white resin, and malic acid. _Datisca
cannabina_[27] contains a coloring matter and another substance
peculiar to itself, datiscin, a kind of starch, or allied to the
glucosides.

Upon the same evolutionary plane among the monocotyledons, the dates
and palms[28] contain in large quantities special starches, and this
is in harmony with the principles of the theory. Alkaloids and
glucosides have not yet been discovered in them.

Other monocotyledonous groups with simplicity of floral elements, such
as the typhaceae, contain large quantities of starch; in the case of
_Typha latifolia_[29] 12.5 per cent., and 1.5 per cent. gum. In the
pollen of this same plant, 2.08 per cent. starch has been found.

Under the dicotyledonous groups, there are no plants with simplicity
of floral elements.

Returning, now, to apetalous plants of multiplicity and simplification
of floral elements, we find that the urticaceae[30] contain free formic
acid; the hemp[31] contains alkaloids; the hop,[32] ethereal oil and
resin; the rhubarb,[33] crysophonic acid; and the begonias,[34]
chicarin and lapacho dyes. The highest apetalous plants contain
camphors and oils; the highest of the monocotyledons contain a
mucilage and oils; and the highest dicotyledons contain oils and
special acids.

The trees yielding common camphor and borneol are from genera of the
lauraceae family; also sassafras camphor is from the same family. Small
quantities of stereoptenes are widely distributed through the plant
kingdom.

The gramineae, or grasses, are especially characterized by the large
quantities of sugar and silica they contain. The ash of the rice hull,
for example, contains ninety eight per cent. silica.

The ranunculaceae contain many plants which yield alkaloids, as
_Hydrastia canadensis_, or Indian hemp, _Helleborus_, _Delphinum_,
_Aconitum_, and the alkaloid berberine has been obtained from genera
of this family.

The alkaloid[35] furnishing families b