MOTION OF THE JUICES. 377 



ments of water, with the production of sugar and other 

 carbhydrates. In the leaves, also, probably nitrogen 

 from the nitrates and ammonia-salts gathered by the 

 roots, is united to carbon, hydrogen, and oxygen, in the 

 formation of albuminoids. 



Besides sugar, malic acid and minute quantities of 

 proteids exist in maple sap. Towards the close of the 

 sugar-season the sap appears to contain other organic 

 substances which render the sugar impure, brown in 

 color, and of different flavpr.. 



It is a matter of observation that maple-sugar is whiter, 

 purer, and "grains" or crystallizes more readily in those 

 years when spring-rains or thaws are least frecjuent. 

 This fact would appear to indicate that the brown or- 

 ganic matters which water extracts from leaf-mold may 

 enter the roots of the trees,. as is the belief of practical 

 men. 



The spring-sap of many other deciduous trees of tem- 

 perate climates contains sugar, but while it is cane sugar 

 in the maple, in other trees it appears to consist mostly 

 or entirely of dextrose. 



Sugar is the chief organic ingredient in the juice of 

 the sugar cane, Indian com, beet, carrot, turnip, and 

 parsnip. 



The sap that flows from the vine and from many cul- 

 tivated herbaceous plants contains little or no sugar ; in 

 that of the vine, gum or dextrin is found in its stead. 



What has already been stated makes evident that we 

 cannot infer the quantity of sap in a plant from what 

 may run out of an incision, for the sap that thus issues 

 is for the most part water forced up from the soil. It is 

 equally plain that the sap, thus collected, has not the 

 normal composition of the juices of the plant ; it must 

 be diluted, and must be the more diluted the longer and 

 the more rapidly it flows. 



TJlbricht has made partial analyses of the sap obtained 



