264 PLANT AND ORGANIC CHEMISTRY 



the numerous genera and species of the vegetable kingdom; 

 though certain compounds frequently occur, as starch, sugar, 

 tannin, and other bodies, correlated in special groups of plants 

 with special and distinct properties. For example, the true 

 starch of the cryptogams will be found gelatinous in Algae, 

 replaced in Fungi as glycogen, and only in the lowest of the 

 flowering plants does it occur in the simplest stratified form; 

 from this stage to the highest of plants, the Composite, in 

 which it occurs as a crystalline substance called inulin, it may 

 be traced from plane to plane of plant-group development in 

 a succession of stratification until it reaches its highest point 

 in our most evolved plants. So strongly marked are these 

 varieties of starch-forms that some investigators, notably 

 Nageli, have proposed this means for the identification of 

 many plant families. 



The many kinds of vegetable sugars known to chemists also 

 have their locations, not only during different stages of the 

 individual plant-growth and in different parts of the plant, 

 as synanthrose, 1 the especial sugar of the unripe grain of rye 

 and wheat, but also in certain families, some one kind of sugar 

 will predominate in many of the individuals. The tannins of 

 the oak, beech, and poplar are not those of the higher plants. 



At a certain stage of plant evolution, glucosides, substances 

 capable of splitting up and yielding, among other products, 

 sugar, appear. I have observed in those plants where large 

 percentages of such substances are found, a diminished pro- 

 portion of starch and sugar, 2 or their absence, notably in soap- 

 bark and species of the Yucca. 



The waxes, oils, camphors, resins, acids, and other classes 

 of vegetable compounds might be similarly cited as offering 

 characteristic properties in various plants in which they appear, 

 but the examples given are ample to illustrate my point, that 

 the chemical compounds of plants should be considered from 

 three sides, viz. : 



i. In their own development through many plant groups, 



1 " Ripening of Seeds," by A. Muntz, Ann. Agronom., xii, 399-400; Jour. 

 Chem. Soc., February, 1887, p. 173. 



2 Trans. Amer. Phil. Soc., "Yucca Angustifolia." See ante, p. 126. 





