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a solution of sugar contained in the protoplasm is the material out of which particles of 

 starch are formed by further chemical and physical changes. The starch is easily 

 changed into sugar by different agencies. From various facts i^e.g. the production of 

 radial fissure-surfaces on drying), it must be concluded that the molecules of starch 

 have not only a definite position in the direction of the radii, but are also arranged tan- 

 gentially in a definite manner in each layer. A lamellar structure and the formation 

 of areolae corresponding to this, appearing as a radial striation, has, however, been ob- 

 served only occasionally and doubtfully. 



Growth by intussusception depends on the permeability of all parts of the grain to 

 water and aqueous solutions. This again can only be explained by supposing that 

 the substance of starch is not continuous, but consists of distinct invisibly minute 

 particles, each of which possesses the power of attracting water, and surrounds itself with 

 an aqueous envelope ; the particles of starch (molecules) are separated from one another 

 by these aqueous envelopes ; the smaller the molecules in a given volume of a starch- 

 grain, the more numerous are these envelopes, and the more watery the volume of 

 starch under consideration. From this it results, on purely mechanical principles, that 

 in this case the aqueous envelopes are thicker, that, on the other hand, as the mole- 

 cules increase in size, they become thinner, and the molecules thus approach nearer 

 one another. The watery layers therefore consist of small molecules which are sepa- 

 rated by thick aqueous envelopes, the denser less watery layers of larger molecules 

 with thinner envelopes. The internal organisation thus depends, in these cases, on a 

 definite co-deposition of water and particles of starch ; the stratification of a starch- 

 grain disappears, like that of a cell-membrane, as soon as the water is removed from 

 it {e. g, by evaporation .or action of absolute alcohol, &c.), because the more w^atery 

 layers then become similar to the less watery, and the difference of refractive power 

 in the two ceases. In the same manner the stratification also disappears when the 

 substance of the grain is rendered capable by chemical means (as weak solution of 

 potash) of absorbing large quantities of water ; the denser layers absorb relatively more 

 water ; they thus become similar to the more watery layers, and it is no longer possible 

 to distinguish between them. 



Besides the abrupt differentiation of the proportion of water which is recognised in 

 the form of stratification, there is also in every grain an increase from without inwards 

 in the amount of water. This is partly ascertained by the refraction, partly by the regular 

 decrease of cohesion from without inwards. If the water is removed from fresh starch- 

 grains, they acquire cleavage-surfaces which cross the layers at right angles; in the 

 interior a cavity is formed from which the fissures radiate ; these become narrower the 

 further they penetrate outwardly ; they are widest* in the middle. From this it follows 

 that on drying the greatest loss of water occurs in the interior, and that this regularly 

 decreases towards the outside ; but it also follows at the same time that the cohesion of 

 the layers is less in the tangential direction (at right angles to the cleavage-surfaces) than 

 in the radial direction ; this points to the conclusion that within every layer the loss 

 of water is greater in the tangential than in the radial direction. 



If the water be removed from a fresh starch-grain or from one saturated with water, 

 it contracts ; the molecules contained in it approach one another when the layers of 

 water between them become thinner. A similar change takes place if the granulose is 

 removed from a grain ; the cellulose-skeleton of the grain which remains is, although 

 saturated with water, much smaller than the intact grain. This possibly results from 

 the fact that the molecules, now consisting only of cellulose, possess less attraction for 

 water, and, having thinner envelopes, approach nearer; the cause may however also 

 be that the number of molecules has diminished. 



(b) The Extraction of the Granulose of starch-grains, leaving behind a skeleton of 

 cellulose, can be brought about in very different ways: — i. By maceration in saliva at 

 an elevated temperature; in the starch of Canna indica the extraction, according to 

 H. von IMohl, is slow at 35-40 C, but is completed in a few hours at 5o"-55 C. ; a lower 



