CHEMICAL BASIS OF PLANT FORMS 251 



the large quantities of sugar and silica they contain. The ash 

 of the rice hull, for example, contains ninety-eight per cent, 

 silica. 



The Ranunculaceae contain many plants which yield alka- 

 loids, as Hydrastis canadensis, Helleboms, Delphinum, Aco- 

 nitum, and the alkaloid berberin has been obtained from 

 genera of this family. 



The alkaloid * furnishing families belong, with few excep- 

 tions, to the dicotyledons. The Liliaceae, from which is ob- 

 tained veratrine, form an exception among the monocotyle- 

 dons. The alkaloids of the fungus have already been noted. 



2 Among the greater number of plant families, no alkaloids 

 have been found. In the Labiatae none has been discovered, 

 nor in the Composite among the highest plants. 



One alkaloid is found in many genera of the Loganiaceae, 

 in genera of the Berberidaceae, Ranunculaceae, Menisper- 

 maceae, Rutaceae, Papaveraceae, Anonaceae. 



Waxes are widely distributed in plants. They occur in quan- 

 tities 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, Cruciferae, Aurantiaceae, Labiatas, and Umbelli- 

 ferae. 



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 mor- 

 phological relations, has been well shown. For example : the 

 similarity 3 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 gen- 

 era of Cactaceae. 



Darwin 4 states that in the Compositae the ray florets are more 

 poisonous than the disc florets in the ratio of about 3 to 2. 



1 Die Pftanzenstoffe, p. 21. 2 Ibid. 



3 Meehan, Proc. Acad. Nat. Sciences. 



* " Different Forms of Flowers on Plants of the Same Species," Introduction. 



