STARCH. 121 
starch-granules are particularly well observable in the first 
stages of germination (Fig. 53). 
We are acquainted with starch in the plant only in the solid 
form, although compelled to assume that it is formed, or ina 
manner crystallizes out, from a liquid. 
Starch forms a glistening powder, the specific gravity of which 
varies according to its origin, but does not deviate much from 
1.5. In the air-dry condition, it incloses from 13 to 17 per cent 
of water, after the removal of which its density increases, accord- 
ing to its derivation, to from 1.56 to 1.63. While air-dry starch 
floats upon chloroform, it sinks therein after having been 
deprived of its water by heating to 100° C. Dried starch quickly 
absorbs again from the air the eliminated water. 
The small amount of incombustible substances which it con- 
sae 
os Gy 4 
Fie. 53.—Corroded starch-granules from the endosperm of a young maize plant 8 
centimeters (about 3 inches) high, in process of solution. a, a granule still intact 
(Tschirch). 
tains, about 0.5 per cent, can 1 probably be explained only by 
supposing them to be deposited mechanically. 
The composition of anhydrous starch corresponds to the 
formula C,,H,,0,,, although Musculus (1861 and 1870) and W. 
Nigeli have shown that the formula O,,H,,0;, or O,,H,,0,, cor- 
responds still better to the facts.* 
Leuchs (in 1831) found that starch granules are attacked by 
saliva. ©. Niigeli, who pursued the subject further, came to 
the conclusion that the granule is built up from cellulose and a 
peculiar starch substance, granulose. According to his view, the 
1 For information relating to the elementary composition of starch, — 
we are indebted to W. Nageli, Sachsse, Pfeiffer, Tollens and Salomon. 
See also Husemann-Hilger, ‘‘ Die Pflanzenstoffe.” 
