STARCH. 285 
find its way from the chlorophyll grains, in which it originates, to 
the cells where it is stored. 
Starch is first formed in the interior of the chlorophyll grains as 
minute, rounded, solid particles. During the whole time the green 
leaves are exposed to sun light, an accumulation of these particles 
occurs in the chlorophyll grains, but as soon as the light fades the 
quantity which hasbeen accumulating all day decreases, and thestarch 
is gradually removed in the form of dextrin, or some other soluble 
form, then on reaching the receptacle in which it is to be stored an 
inverse change ensues and the dextrin is once more converted into 
starch, in which form it is deposited. Although the process of 
removal of the original particles of starch from the chlorophyll 
grains can be traced only at night, it, in all probability, goes on 
constantly, but during the daytime the rate of removal is insufficient 
to counterbalance the larger amount of new material formed. 
In the chlorophyll grains the particles of starch never reach any 
higher degree of organisation than that mentioned above, but in 
the stems, tubers, roots, rhizomes, seeds, and other parts where it 
is stored for future use, it assumes the form of complex and 
definitely-organised grains, whose form is characteristic of the 
genus or species in which they occur. The grains are frequently 
of a large size, but the size varies considerably, being in some 
plants almost immeasurably minute, in others as the Potato and 
Tous-les-mois, attaining a diameter of as much as a four-hundredth 
of an inch, and being readily visible with a simple lens. In the 
same plant, and even the same cell, the size varies considerably, 
being dependent chiefly on the relative age of the grains, so that 
when measures of starch grains from various sources are given, 
they must be taken only to represent an average, and much latitude 
must be allowed for individual variation. In some plants, though 
—the Sarsaparilla for instance—the variation in size is less marked. 
The forms of the starch grains are as variable as their sizes. In 
the potato they are oval, in the bean elliptical, in some orchids 
spherical, in the wheat grain lenticular, in the maize polyangular, 
in ginger root, like short bent rods, and in the laticiferous cells of 
Euphorbia peculiar bone-like forms occur. In the oat the grains 
are compound, consisting of a number of closely packed, but 
readily separable, granules. 
Examined under a sufficiently high power, and in a suitable 
medium (50 per cent. glycerine answers well), a dark spot will be 
seen in most grains. This is called the hilum or nucleus and is 
usually placed eccentrically. In those grains which are elliptical, 
it is placed nearest the narrow end of the grain. Surrounding the 
hilum will be observed a number of zones, alternately light and 
dark, due to alternations of more and less watery layers, and 
besides these alternations of much and little water in the layers, 
