FOOD AFTEK GEBMIITlTIOlir. 367 



up some other elements of its nutrition to which it has 

 immediate access. Leaving but of view, for the present, 

 those matter's which, though found in the plant, appear 

 to be unessential to its growth, viz., silica and sodium 

 salts, the roots absorb the following substances, viz. : 



Sulphates 1 f Potassium, 



Phosphates 



Nltiates and 



Chlorides J L Iron. 



. I Calcium, 



1 Magnesium and 



These salts enter the plant by the absorbent surfaces 

 of the younger rootlets, and pass upwards, through the 

 stem, to the leaves and to the new-forming buds. 



The Leaves, which are unfolded to the air, gather 

 from it Carton dioxide Gas. This compound suffers 

 decomposition in the plant ; its Carbon remains there, 

 its Oxygen or an equivalent quantity, very nearly, is 

 thrown off into the air again. 



The decomposition of carbon dioxide takes place only 

 by day and under the influence of the sun's light. 



Prom the carbon thus acquired and the elements of 

 water with the co-operation of the ash-ingredients, the 

 plant organizes the Carbhydrates. Probably some of the . 

 glucoses are the first products of this synthesis. Starch, 

 in the form of granules, is the .first product that is 

 recognizable by help of the microscope. 



The formation of carbhydrates appears to proceed in 

 the chlorophyl-cells of the leaf, where starch-granules' 

 first make their appearance. 



The Albuminoids require for their production the 

 presence of a compound of Witrogen. The salts of 

 Nitric A cid (nitrates) are commonly the chief, and may 

 be the only, supply of this element. 



The other proximate principles, the fats, the alkaloids, 

 and the acids, are built up from the same food-elements. 

 In most cases the steps in the construction, of organic 

 matters are unknown to us, or subjects of uncertain con- 

 jecture. 



