Heckel's[19] scheme of plant evolution. All these plants are grouped
under three main divisions: apetalous, monocotyledonous, and
dicotyledonous; and these main divisions are further subdivided.
It will be observed that these three main parallel columns are divided
into three general horizontal planes.
On plane 1 are all plants of simplicity of floral elements, or parts;
for example, the black walnut, with the simple flower contained in a
catkin.
On plane 2 plants which have a multiplicity of floral elements, as the
many petals and stamens of the rose; and finally, the higher plants,
the orchids among the monocotyledons and the composite among the
dicotyledonous plants, come under the third division of condensation
of floral elements.
It will be impossible to take up in order for chemical consideration
all these groups, and I shall restrict myself to pointing out the
occurrence of certain constituents.
I desire now to call attention to chemical groups under the apetalous
plants having simplicity of floral elements.
_Cassuarina equisetifolia_[20] possibly contains tannin, since it is
used for curing hides. The bark contains a dye. It is said to resemble
_Equisetum_[21] in appearance, and in this latter plant a yellow dye
is found.
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