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Starches. Case 69.—Starch is largely formed by most 
plants, as a reserve food supply, from the water taken in 
through the roots and the carbonic acid gas inhaled from 
the etmOspnEre, the chemical combination is effected by 
the sun’s energy, directed by the green coloring matter 
(chlorophyl). Starch is mostly found in the form of 
granules, sometimes in small rods, and is easily converted 
by the plant, or artificially, into glucose, in which form 
the plant consumes it. In darkness the plant consumes 
starch previously formed in daylight. Starch is insoluble 
in water and can therefore be easily washed out from ground 
plant tissue. The forms of the starch grains are so con- 
stant and characteristic in each plant that they afford an 
excellent method of identifying the latter, even in powder. 
Starch, as in the case of many other substances, exists in 
and is consequently derived from the several organs of 
various plants, for example, the roots of the cassava plant 
furnish the cassava flour and tapioca, while those of coontie 
yield coontie floor or Florida-arrowroot which is quite 
similar to sago, and those of the sweet-potato plant furnish 
sweet-potato flour. The rootstocks of the common potato 
plant abound in potato-flour, while those of the arrowroot 
plant yield arrowroot flour. The stems of some of the 
sago palms and those of some of the true palms are the 
sources of sago flour. The fruits, both dry and fleshy, of a 
great variety of plants, contain starch; for example, those 
of the several grains, wheat, rye, and corn; while those of 
the banana yield the less common banana flour. The 
seeds of some plants are used as a source of starch, as for 
instance, those of the chocolate plant 
Cork and Paper. Cases 70 and 72. Cork forms the 
outer portion of the bark of most woody stems. That of 
one species of oak, Quercus Suber, of the Mediterranean 
region, possesses peculiar properties of toughness, elas- 
ticity, and imperviousness to liquids and vapors which 
makes it useful for bottle stoppers. Many attempts have 
been made to find substitutes, but none have been found 
