io8 The Living Plant 



it occurs in the various roles above mentioned for grape sugar. 

 It is sweeter than grape sugar but ferments less easily. Chem- 

 ically it is called fructose, and has the formula C 6 H 12 6 , differing 

 from grape sugar not in the kind or number of atoms entering into 

 its composition, but in the arrangement of these within the mole- 

 cule, as best demonstrated by physical tests with polarized light. 



Cane Siigar. This substance is perfectly familiar to everybody, 

 for it is the granulated sugar of the table. It is widely spread 

 through plants dissolved in the sap, and accumulates in some kinds 

 so abundantly as to form a reserve supply of food for them, and 

 a store upon which animals, inclusive of man, are accustomed to 

 draw for their needs. This accumulation occurs conspicuously in 

 the Sugar Cane and the Sugar Beet (both of which plants have 

 had then* percentage of sugar immensely increased by cultivation), 

 hi the Maple tree, and in a few other less conspicuous plants, 

 while it is common as well in ripening fruits. Chemically cane 

 sugar is called sucrose, and has the formula C 12 H 22 O n . It is 

 built up by living protoplasm from photosynthetic sugar through 

 this simple step, 2 C 6 H 12 6 -H 2 (water) =C 12 H 22 O n ; and it falls 

 back by a reverse process to a molecule of grape sugar and one of 

 fruit sugar. This latter. step actually occurs in the ripening of 

 fruits, in cooking, and in digestion; and it is, therefore, as grape 

 sugar or fruit sugar that cane sugar is finally incorporated into 

 both the plant and the animal body. 



In addition to these sugars, there are others of rarer sort de- 

 scribed in the technical books, all closely related and more or 

 less intertransformable into those we have mentioned. Such are, 

 for example, maltose, mannose, galactose, arabinose, xylose, 

 fucose. I am very well aware that these names will have no great 

 attraction for the reader, but I take somewhat the same satis- 

 faction hi their recital that Homer derived from the roll of his 

 heroes, whom also he mentions but once. 



Starch. This substance is perfectly familiar to everyone as 

 common laundry starch, and especially as flour, which is mostly 



