THE WORK OF LEAVES 165 



solution; a red precipitate, or sediment, indicates the 

 presence of grape-sugar; the precipitate may not 

 appear until the boiled solution has been allowed to 

 stand for a time. (Cane-sugar may be tested for, if 

 desired, by the methods described in works on chem- 

 istry; it is found in seeds to such a small extent that 

 it may be neglected.) 



Fats and oils, whenever abundant, will ooze out 

 if a pin is stuck into the dry seed-leaf; a better 

 method consists in powdering the substance of the dry 

 seed-leaf (scraping with a knife usually suffices for 

 this) and placing it on a piece of paper on a clean 

 plate in a warm oven (not hot enough to scorch the 

 paper) ; the oil, if present, will make a spot on the 

 paper. Very small quantities of oil may be detected 

 by grinding up the seeds and extracting with benzine 

 (or gasolene, ether, chloroform, etc.); on standing, 

 the benzine will evaporate, leaving the oil. Care must 

 be taken in using benzine (or the other substances 

 mentioned) not to bring it near a flame or stove, as 

 the vapor is highly inflammable. 



Proteids may be tested for by nitric acid, a drop of 

 which should be placed on the seed-leaf; it may be 

 followed by a drop of ammonia to intensify the color. 

 A yellow color indicates the presence of proteid sub- 

 hydrate (soda lye) in water to make Solution II. To make up the reagent, 

 add to a given quantity of Solution I two and one-half times its volume of 

 Solution II, and one and one-half times its volume of water. Make up the 

 reagent fresh whenever needed. 



