1917] FAUST—RESIN SECRETION 461 
tests for fatty oils. In the roots of young plants (two years or 
less) it is found mostly in the outer ring of canals, while in old roots 
it occurs in the two concentric rings of canals, together with the 
radial anastomoses. 
As has previously been mentioned, the ordinary resin tests are 
cupric acetate and alkannin tincture. The acetate requires several 
days and imparts a brilliant emerald to the resin. The alkannin 
causes the resin to take on a brilliant crimson in a very short time. 
The resin may be distinguished from oils of a fatty nature by the 
osmic anhydride test. The alkannin is much more soluble in the 
higher grades of alcohol, but such a high concentration of the solvent 
is not desirable, since it also acts as a ready solvent for the resin. 
The Tscurrcu test for resin, modified from MUELLER, was used 
by Tscuircu for demonstrating that resin was present in the lumina 
of canals of Imperatorium Ostruthium, Arnica montana, Abies pec- 
tinata, and A. Normanni. In fact, TscutrcH noted a layer of slime 
among all schizogenously formed canals. The writer has made use 
of this technique for testing resin in B. sagittata and Parthenium 
argentatum. These preparations show resin in the canals, as 
described by Tscutrcu, but in addition demonstrate resin in the 
newly formed xylem, an abundance of it in rays and inner regions 
of cortex, including the cells immediately surrounding the canals, 
and great masses of resin in the cambium. Such dry preparations 
demonstrate resin in the identical locations as the aqueous mounts 
from fresh material and alcoholic material. In this wise an accurate 
check has been secured on the demonstration mounts. 
An analysis was then made to discover the approximate relation 
of resin to other organic materials. Resins are classified according 
to their reactions to four kinds of tests: resino-tannol, resene, 
resiniferous oil, and resinic acid tests. 
The resino-tannols are those resiniferous materials which react 
to tannin tests. For example, when ferric chloride is added to a 
solution of resino-tannol, iron tannate is formed as a precipitate. 
Other reagents used to test this relationship are potassium bichro- 
mate, lead acetate, potassium hydrate in alcoholic solution, and 
nitric acid. Should any of these reagents give a positive test, an 
exceedingly difficult problem would then confront the investigator. 
