HIGHER AND LOWER PLANTS 
273 
to the solvent action of saponin on resins, 1 also on calcium 
oxalate. This property is of value to the plant not only by act¬ 
ing as a solvent of insoluble or slightly soluble compounds, and 
thus assisting it in obtaining food otherwise difficult of access, 
but also resins are found in nearly all the Lirioideae, and the 
presence of this chemical class associated with saponin shows 
a physiological adaptation of importance to the plant. It may 
be recalled that the pink family is remarkable for its proportion 
of lime, and this element is frequently found in large quantities, 
as well as resins, in other saponin orders. Saponin may thus be 
called a constructive element in developing the plant from the 
multiplicity of floral elements to cephalization of these organs. 
Among the members of the higher groups of plants many of 
the preceding stages of chemical evolution are represented up to 
a certain point, when the plants acquire other chemical charac¬ 
teristics, — i.e., indigo, haematoxylin, and other coloring-mat¬ 
ters of the leguminous groups, and the dyes of the madder plant, 
give way to the alkaloids of the cinchona, the coffee, the atropa, 
and the strychnos orders, and to the organic acids of the vale¬ 
rian order, and the aromatic and volatile compounds of the 
Compositae. 
Alkaloids, though so widely distributed, are not found in the 
very lowest or the highest plants. Their occurrence in fungi 
has been already noted. In flowering plants, among the lower 
apetals, piperin, the alkaloid of Piperaceae, occurs; also, alka¬ 
loids are found in the monimia, hemp, laurel, and amaryllis 
orders, and in colchicum; but they are exceptional in these 
lower groups, and belong properly to dicotyledons, where they 
are found in many orders. 
Besides the occurrence of compounds peculiar to distinct 
plants, or whole plant groups, another class is found, and the 
substances of this class may be scattered quite generally through 
the plant kingdom, but always associated with some other com¬ 
pound. 
Coumarin, the odorous principle of tonka-bean and vernal 
grass, is one illustration; its occurrence is limited to those plants 
1 “Yucca Angustifolia,” Trans. Amer. Phil. Soc., see p. 126; “Chemical 
Basis of Plant Forms,” Journal Franklin Institute. See p. 232. 
