72 



POPULAR ECONOMIC BOTANY. 



French schools. However, Payen, Persoz, and Fritsche, 

 eminent investigators of this highly important point in ve- 

 getable physiology, assert quite the contrary. According 

 to these physiologists, starch granules are made up of con- 

 centric laminae, which are superimposed upon one another, 

 and that both their exterior and interior parts consist of the 

 same material, being a substance peculiar to the vegetable 

 kingdom, insoluble in cold water, but capable by heat of 

 being converted into soluble sugar and gum. 



Starch is the nutritive matter of plants, which, like the 

 bees, lay up a store for the winter season ; but as light has 

 the effect of converting it into chlorophyle, or the green 

 colouring matter of plants, nature designs that the reserve 

 store shall usually be deposited in the underground roots, 

 removed from the influence of the sun^s luminous rays. 

 Here its quality of being insoluble in cold water is of im- 

 mense importance, because, if soluble, the rains of winter 

 would dissolve and wash out the store thus laid up, — from 

 this it is protected by its insolubility ; but when the warmth 

 of spring and the vitality of the plant begin to operate upon 

 the starch-granules, they are converted into sugar and gum 

 by the influence of a peculiar ferment called diastase ; after 

 this conversion they are easily soluble in the juices of the 



