262 PLANT AND ORGANIC CHEMISTRY 
These ash-ingredients are usually present in each plant 
cell, in the cell wall, imbedded in the cellulose and partly in the 
contents of the cell. The salts of the alkaline metals, sul¬ 
phates, chlorides of magnesium and calcium, also soluble 
silicic acid, as in Equisetum hiemale / occur in solution in 
the cell-sap, and insoluble salts exist in the tissues of plants. 
The differences in the composition of the ash of plants show 
that each plant is endowed with a specific absorbent capacity; 
thus a gramineous plant 2 is able to withdraw relatively larger 
quantities of silica from the soil than a leguminous plant. 
The latter can only do so to a very slight extent. 
The absorbent capacities of allied species are very different. 
Again, individuals of the same species yield different ash-con¬ 
stituents, depending upon their vigor, and at different periods 
of growth the ash-composition varies. In a summary of experi¬ 
mental results it has been stated that 3 “ similar kinds of plants, 
and especially the same parts of similar plants, exhibit a 
close general agreement in the composition of their ashes, 
while plants which are unlike in their botanical characters 
are also unlike in the proportions of their fixed ingredients.” 
Certain marked varieties of plants appear to be peculiar 
to and developed by certain soils, as the violet, var. calami - 
naris, and the penny cress, in zinc soils. 4 In the leaves of the 
latter plant thirteen per cent, of zinc oxide was found, and I 
have found manganese in the different portions of Yucca 
anguslifolia 5 grown near Lake Valley, New Mexico. 
Plants may absorb from the soil mineral matters independ¬ 
ently of their use or harmfulness to the plant, but the ab¬ 
sorption of essential inorganic constituents will depend upon 
their relation to the changes in the vegetable cell. 
The ash-constituents of a plant increase from the roots 
upward to the leaves, the largest percentage being found in 
the younger portions of the growing plant, and I have ob¬ 
served this same principle on a more general scale running 
1 Lange, Ber. d. Deut. Chem. Ges ., xi. 
2 Wolff, Aschenanalysen, 1871. 
3 How Crops Grow , by S. W. Johnson, London, p. 145. 
4 A. Braum and Risse, Sachs, Exp. Physiologie , p. 153. 
5 Amer. Phil. Soc. Trans., H. C. De S. Abbott. See ante , p. 126. 
