140 THE CHEMISTRY OF THE PLANT 
Carbonic 
H.CO; 
Silicic (of various forms) 
Si(OH).4, ete. 
Organic Acids. 
Formic 
CH2O2, (HCOOH) 
Acetic 
C.H.O2, (CH;COOH) 
Butyric (normal) 
C4,HsO2, (CH; -CH:—CH:2 — 
COOH). 
As CaCO; in eystoliths of 
Ficus, and as deposits in or 
upon the cell walls of many 
algae and fungi. 
These are absorbed in the K, 
Na and Al salts and are some- 
times deposited in undeter- 
mined composition in cell 
walls, e.g. diatoms, scouring 
rushes (Equisetum), ete. 
These occur in all parts of the 
plant, either free or as esters 
or as salts of metallic bases. 
They are present as reserve 
food, as waste products, as 
substances to increase the os- 
motic pressure, to increase 
acidity, ete. 
As free acid in stinging hairs 
of nettles, in some fruits, etc., 
and sometimes as salts of 
various metals. 
As salts of various metals in 
the cell sap. Formed as free 
acid by the fermentation of 
ethyl alcohol by various bac- 
teria. Produced in dry distil- 
lation of wood. 
As esters in various Apiaceae. 
Isobutyric Free in fruit of St. John’s 
CH; bread (Ceratonia siliqua) and 
C,HsO2, CH—COOH)in various other plants. 
CH; 
Palmitic, Stearic and Oleic (see below under fats). 
Glycollic 
C2H,O;, (CH.(OH) —COOH) 
In unripe fruits and leaves of 
the grape. 
