elong, with few exceptions, to
the dicotyledons. The colchiceae, from which is obtained veratrine,
form an exception among the monocotyledons. The alkaloids of the
fungus have already been noted.

[36]Among the greater number of plant families, no alkaloids have been
found. In the labiatae none has been discovered, nor in the compositae
among the highest plants.

One alkaloid is found in many genera of the loganiaceae; berberine in
genera of the berberidaceae, ranunculaceae, menispermaceae, rutaceae,
papaveraceae, anonaceae.

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 myrtaceae, laurineae, cyperaceae,
crucifereae, aurantiaceae, labiatae, and umbelliferae.

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 cactaceae and
portulaceae, 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 cactaceae.

Darwin[38] states that in the compositae the ray florets are more
poisonous than the disk florets, in the ratio of about 3 to 2.

Comparing the cycadeae and palmae, 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