16 THE NATURE-STUDY OF PLANTS 
we have another vital point of agreement in the lives 
of plants and ourselves. 
I want the student, as I have said, to see things for 
himself, and there is no difficulty about the ocular 
demonstration of starch grains in the plant body. 
He should take, and place upon a white china 
saucer, a small slice, about an eighth of an inch thick, 
of a raw potato or the thick, root-like stem of the Blue 
Flag that creeps along or just below the surface of the 
soil in our gardens: it is better for this purpose than 
the Yellow Flag because of the whiteness of its flesh. 
Sufficient pressure must be applied to squeeze out 
some of the moisture and then a little weak solution of 
iodine in water must be added. The result will be 
that the slice will change colour and turn a light or 
a darker blue according to the strength of the solution. 
Clusters of grains of the same colour will be found in 
the surrounding liquid ; but all starch grains are tiny 
little things, and the student will have to use a micro- 
scope should he determine to make out their form for 
himself, for the solution will enable 
him to see them only in clusters, 
but not individually even with a 
lens ; they are usually more or less 
round or oval, so I illustrate those 
of the Petty Spurge, which are of 
a very different shape. 
There is a very remarkable fact 

Fic. 4.—Starch grains 
of Petty Spurge. that I must not omit about starch 
A, the longest one observed, grains. We constantly see adver- 
measured shy Of aninch. ticoments of “manufacturers” of 
starch, but the real truth is that 
nobody in the world knows exactly how it is pro- 
duced. Instead of being manufactured by men, all 
