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Page 38
Waxes are widely distributed in plants. They occur in quantities in
some closely related families.
Ethereal oils occur in many families, in the bark, root, wood, leaf,
flower, and fruit; particularly in myrtace�, laurine�, cyperace�,
crucifere�, aurantiace�, labiat�, and umbellifer�.
Resins are found in most of the higher plants. Tropical plants are
richer in resins than those of cold climates.
Chemical resemblance between groups, as indicating morphological
relations, has been well shown. For example: the similarity[37] of the
viscid juices, and a like taste and smell, among cactace� and
portulace�, indicate a closer relationship between these two orders
than botanical classification would perhaps allow. This fact was
corroborated by the discovery of irritable stamens in _Portulaca_ and
_Opuntia_, and other genera of cactace�.
Darwin[38] states that in the composit� the ray florets are more
poisonous than the disk florets, in the ratio of about 3 to 2.
Comparing the cycade� and palm�, the former are differently placed by
different botanists, but the general resemblance is remarkable, and
they both yield sago.
Chemical constituents of plants are found in varying quantities during
stated periods of the year. Certain compounds present at one stage of
growth are absent at another. Many facts could be brought forward to
show the different chemical composition of plants in different stages
of growth. The _Thuja occidentalis_[39] in the juvenescent and adult
form, offers an example where morphological and chemical differences
go hand in hand. Analyses of this plant under both conditions show a
striking difference.
Different parts of plants may contain distinct chemical compounds, and
the comparative chemical study of plant orders comprises the analysis
of all parts of plants of different species.
For example; four portions of the _Yucca angustifolia_[40] were
examined chemically; the bark and wood of the root and the base and
blades of the leaves. Fixed oils were separated from each part. These
were not identical; two were fluid at ordinary temperature, and two
were solid. Their melting and solidifying points were not the same.
This difference in the physical character and chemical reaction of
these fixed oils may be due to the presence of free fatty acid and
glycerides in varying proportions in the four parts of the plants. It
is of interest to note that, in the subterranean part of the _Yucca_,
the oil extracted from the bark is solid at the ordinary temperature;
from the wood it was of a less solid consistency; while the yellow
base of the leaf contained an oil quite soft, and in the green leaf
the oil is almost fluid.
Two new resins were extracted from the yellow and green parts of the
leaf. It was proposed to name them _yuccal_ and _pyroph�al_ An
examination of the contents of each extract showed a different
quantitative and qualitative result.
Saponin was found in all parts of the plant.
Many of the above facts have been collected from the investigations of
others. I have introduced these statements, selected from a mass of
material, as evidences in favor of the view stated at the beginning of
this paper.[41] My own study has been directed toward the discovery of
saponin in those plants where it was presumably to be found. The
practical use of this theory in plant analysis will lead the chemists
at once to a search for those compounds which morphology shows are
probably present.
I have discovered saponin in all parts of the _Yucca angustifolia_, in
the _Y. filimentosa_ and _Y. gloriosa_, in several species of agav�,
and in plants belonging to the leguminos� family.
The list[42] of plants in which saponin has been discovered is given
in the note. All these plants are contained in the middle plane of
Heckel's scheme. No plants containing saponin have been found among
apetalous groups. No plants have been found containing saponin among
the lower monocotyledons.
The plane of saponin passes from the liliace� and allied groups to the
rosales and higher dicotyledons.
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