M. Martin on the Amylum Grains of the Potatoe. 283 



centre, appears to be physically impossible. That the internal 

 layers boil away to a kind of jelly and become liquid, or at least 

 mucilaginous, is also in opposition to the so often proved homo- 

 geneousness of the amylum substance. In short, the fact that a 

 grain completely pressed to pieces, when boiled under the micro- 

 scope, is seen to swell up in all its fragments, each of which 

 forms a rag of transparent skin, is alone sufficient to answer all 

 these questions in the negative. 



Fritsche's opinion, that the internal layers escape when the 

 external skin bursts, appears, considering the above, to be quite 

 inadmissible. What, then, becomes of the layers ? The new 

 theory here propounded easily and satisfactorily answers the 

 question — they unfold themselves. Of this the microscope will 

 furnish the proof. As soon as the observer has learnt to follow 

 the rapid progress of boiling, he will be able distinctly to see 

 the separation of the seam where the edges of the bands are 

 united; he will see immediately after this, that the folds thus 

 laid free are pressed forward, spread out, and in large grains arc 

 laid in a wreath of folds around the flatter central part. While 

 the bauds are shrinking back, the interior edge thus being 

 loosened is not visible, which is very natural, because a double 

 vesicle has been rolled up, the external skin of which on unfold- 

 ing is drawn over the internal one, and the real edge is thus 

 concealed. 



The longitudinal wrinkle generally seen in the boiled grains 

 cannot be easily accounted for on the old system. But according 

 to the new one, it appears that the vesicle which has been rolled 

 up and kept in tension is extended all round ; and when laid up 

 flatly in its watch-glass-like shape produces a fold, wide in the 

 middle and pointed at both ends, which, with ovate vesicles, 

 exactly coincides with their long axes, precisely as observation 

 demonstrates. 



I have before remarked, that during the growing together of 

 the bands, the parts around the so-called kernel must be con- 

 densed, a supposition also verified by observation ; for no sooner 

 does the smaller band separate, tban the grain, especially a large 

 one, extends with a jerk, as though forced by a spring just libe- 

 rated. The external appearance, even of the layers, with their 

 angular and frequently broken forms, is more in accordance with 

 their rolling up than with their free formation. 



As to the Dumber of layers, four full windings would, as the 

 vesicle is double, produce seventeen apparent layers, without 

 counting the bends, which most probably are produced parallel 

 to the windings in the inside, and which to the eye appeal' like 

 layers. 



finally, let m- consider the ph;enonien;i when the grains arc 



