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STARCH. PART II. 



forms water. Many of them have precisely the same 

 quantity of carbon, and only differ in the quantity of 

 the aquatic element, as for example, lignin, starch, and 

 cane-sugar, which consist of 12 parts of carbon, in a 

 state of combination with 8, 10, and 11 parts of water 

 respectively ; indeed the affinity between many of these 

 neutral hydrates is of a most intimate character. Some 

 of their varieties are isomeric, that is to say, they 

 contain the same ingredients in the same proportions, 

 and yet they differ essentially in regard to their pro- 

 perties. 



Next to cellulose, starch is the most universal and 

 distinctive of vegetable productions, being a constituent 

 of all plants, except the fungi. It abounds in the grains 

 and other seeds, and supplies the young plant with food 

 till it can feed itself. In both of the flowering classes 

 it occurs in small colourless transparent grains, either 

 floating in the sap, attached to the walls of the cells, or 

 accumulated within them. Starch globules of very 

 small size are imbedded, either singly or in groups, in 

 the granules of chlorophyll, or leaf green ; the manner 

 in which the green coating takes place is unknown. 

 Starch is an organic substance, varying from grains of 

 inappreciable minuteness to such as are visible to the 

 naked eye, and of such a variety of forms that it can be 

 ascertained with tolerable certainty by what plant a 

 grain of starch has been produced. The small grains 

 are generally globular, but whatever the form may be, 

 each consists of a series of superimposed layers of differ- 

 ent densities, which exhibit coloured rings and a black 

 cross in polarized light. 



Starch is an early and transient product of young 

 plants, which is destined to be changed into nutritious 

 substances at a later period, but being insoluble in cold 

 water it is unfit to travel with the sap. However a 

 ferment called diastase produced during the incipient 

 germination of the grains and seeds, in the tubers of 



