2Ö4 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 Compositae, 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 
Nägeli, 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. 
