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 amaryUis 

 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. 



