The _Myrica_[22] contains ethereal oil, wax, resin, balsam, in all
parts of the plant. The root contains in addition fats, tannin, and
starch, also myricinic acid.
In the willow and poplar,[23] a crystalline, bitter substance, salicin
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.
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