INTERNAL STRUCTURE OF PLANTS. 
17 
vulgaris, fig. 12. Large and small granules of starch are 
generally mixed with each other. The most external cells of 
the grain of wheat, in which, according to Payen, the most 
gelatine is contained, contain small granules of starch, as if 
they were developed from gelatine. Mold, I think, was the first 
who observed that starch developes itself in chlorophyll ; it 
may he observed, with peculiar distinctness, in the older leaves 
of the Vallisneria spiralis, where a granule of starch is pro- 
duced in the granules of chlorophyll, as may he perceived by 
the application of iodine. It is remarkable, that the movement 
of the chlorophyll granules immediately ceases, as soon as a 
granule of starch has formed itself in them. 
Vegetable substances are by no means so uniform as the 
mineral substances. Saltpetre is saltpetre, and common salt 
common salt, let it be prepared in what way it will, if 
it has only been properly cleansed. This is not the case 
with many vegetable substances — for instance, with alcohol, 
the vegetable acids, &c. In others, this chemical universality, 
if I may so term it, is not so great as is seen in sugar. The 
vegetable substances, indeed the organic substances in general, 
only form genera and species in most cases. Thus the etheric 
oils are different in every kind of plants, and this is also the 
case with the isomeric compounds ; also with the resins and 
gums ; and although they have but five distinguishing charac- 
ters, yet they differ in their qualities in almost every plant. 
This is also the case with starch, for although it has the same 
characters from wheat, potatoes, and from arrow root, yet 
the jelly obtained from them exhibits differences. Potato 
starch, for instance, has a peculiar smell. In this instance, 
therefore, as indeed is done generally in natural history, we 
reduce the species into genera, which we distinguish by cer- 
tain marks ; and thus every thing is called starch, which pre- 
sents itself unformed or in granules, that assumes a blue colour 
on the application of iodine, and that is dissolved in warm 
water ; and not in spirit of wine, ether, and oils. The Althaea 
mucus also, at least partially, belongs to the genus starch; 
it forms granules, which become blue on the application of 
iodine, which dissolve themselves in cold water, and which 
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