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ON STARCH. 
In small spherical grains this is the case, but when the 
number of layers increases with growth, they increase in 
width more rapidly in the direction of the axis of the grain. 
The growth of starch grains is accomplished exclusively by 
intussusception, new particles being thrust in between the 
layers already existing both radially and tangentially, the 
proportion of water at the particular places being at the same 
time changed. 
Classification of Starches. 
The examination of starches by the microscope requires 
practical study; drawings and descriptions must be used as 
guides merely. It is not easy to preserve starches mounted 
as microscopical objects. Glycerine is the best medium. 
A high magnifying power is not generally required, except 
for such as rice and pepper. The best powers are J, and 
with micrometer eye-piece. The value of the micrometer 
scale must be of course ascertained by comparing the 
divisions with those of a stage micrometer graduated in 
hundredths and thousandths of an inch. In illuminating 
the object oblique light is best, when the rings are best seen. 
The polariscope is very useful, as many starches yield black 
crosses, which are characteristic, e.g ., potato. Dr. Muter 
has arranged the starches in five classes, according to the 
following characters :— 
Class I.—The liilum and concentric rings clearly visible; 
all the starches oval or ovate. This group includes tons les 
mois, potato, arrowroot, calumba, orris, galangal, and tur¬ 
meric. 
(1.) Tous les mois or Canna arrowroot. The granules 
vary from *0037 to *00185 inch. In shape they 
are ovoid when small. The largest are oval, with 
pointed ends. Hilum annular eccentric ; rings 
incomplete, very fine, narrow ; with polarised light 
the cross is more regular than that of potato starch. 
(2.) Arrowroot (Jamaica) from Maranta arundinacea gran¬ 
ules ovoid, flattened, tending to triangular form 
in larger and round in smaller, rings visible and 
numerous, not very marked ; size, *00138 inch. 
(3.) Potato (Solanum tuberosum). Granules vary in 
shape and size, some small and circular, others 
large, ovate, and oyster shaped. Hilum annular, 
and rings incomplete. In large grains, rings 
numerous and distinct. Size, *0027 to *00148 inch. 
Eccentricity averages 
