STARCH. 



73 



plants and are carried into circulation for the nutrition of 

 the new vegetation. These operations are not merely chemi- 

 cal ; they depend also upon the vitality of the plant. Dr. 

 Charles Inman, of Liverpool^ in a paper read before the 

 Literary and Philosophical Society of that town,, has shown 

 that the fall of the leaf, one of the most singular pheno- 

 mena of vegetable Kfe, is caused by the deposit of a ring 

 of starch-globules at the base of the petiole, where it is ar- 

 ticulated to the stem ; this ring, continuing to increase in- 

 ternally, eventually cuts through the petiole, and so dissevers 

 the leaf from the plant. May we not then assume that the 

 decreasing influence of the sun towards autumn, and the 

 exhausted vitality of the plant, acting together, prevent the 

 conversion of the starch, formed by the secretory cells of 

 the leaf, into chlorophyle, and hence the leaf loses its green 

 colour, becomes yellow or red, and finally, from the deposit 

 of starch in its petiole, falls to the ground? We have 

 however much to learn respecting the nature of starch ; even 

 the form of the granules, in different species of plants, is 

 a matter of much dispute, and most authors give different 

 delineations (we give two in Plate XI. fig. 56, 57, from 

 good authorities). 



When perfectly pure, all starch is the same in appearance 



