10 



the microscope is a reliable guide, often enabling us 

 to refer the Starch, not only to the natural order of 

 the plant producing it, but also to the genus and 

 species. 



The chemistry of Starch, its relation to chlorophyll, 

 its method of growth, and the part it plays in vegetable 

 nutrition, are dealt with in most works on Vegetable 

 Histology and Physiology, and any one requiring 

 further information on this part of the subject will find 

 it exhaustively treated in Sach's " Text Book of 

 Botany," and more concisely in Thome's " Structural 

 Botany." Its physical structure has been a subject of 

 much discussion among Botanists, and there still 

 appears to be room for further investigation. 



The theory of its formation in layers round a central 

 point called the hilum, thus giving rise to the concentric 

 lines, has given way to the belief that it is formed by a 

 process of intussusseption, similar to that of the 

 thickening process of the cell wall, and that the 

 markings are due to the unequal distribution of water, 

 thus producing the appearance of layers. The reason 

 given by Thome for this hypothesis is that perfectly 

 dry Starch grains are unstratified. But the author has 

 a preparation of Starch from the fruit of the Potato 

 mounted without water treatment in a solution of Gum 

 Dammar, in which the markings are distinctly visible. 



Anyone wishing further to investigate this matter 

 will find an excellent Starch for experiment in the pulpy 

 part of the nearly ripe fruit of the Potato, an illustra- 



