462 BOTANICAL GAZETTE [DECEMBER 
Since tannin is not a single compound, but a convenient name for 
a related group of compounds, separate tests of the entire group 
would then be necessary. Moreover, as Tscutrcu has pointed out 
(loc. cit. 1142), such a test would not necessarily prove a genetic 
relationship, since tannin might be merely a en and not 
its source. 
Samples of the resin (ether eetractiod) from B. sagittata were 
submitted to the resino-tannol tests. All samples gave negative 
test except the one where nitric acid was used as the reagent, in 
which case the test was atypical. This test was so positive, how- 
ever, that it served to indicate a possible relationship of another 
nature. Two or three drops of the pure resin were placed in con- 
centrated nitric acid. The resin globules became dark brown, with 
a violent evolution of nitric oxide in the course of two minutes, 
accompanied by the formation of a cellulose membrane across the 
top of the solution. When heated, this membrane burned with a 
warm yellow flame and heavy smoke, leaving a black char. The 
odor was like that of burning celluloid. The test was then repeated 
with resin dissolved in 95 per cent alcohol. The reaction was 
delayed, not taking place for 5 minutes, but was accompanied by 
a more violent evolution of the gas. When the test was repeated 
with the resin dissolved in absolute alcohol, the test reaction did 
not take place for 6 minutes, and was even more violent than on 
either of the previous occasions. Such a reaction would indicate 
a relationship to cellulose or other carbohydrate. 
The second group of resins are called resenes. They are the 
ones showing kinship to the terpenes and the fatty aldehydes. The 
modified cholesterol tests are applied to these substances. Two of 
the more common and specific ones are the Salkowsky-Hesse and 
Mach reactions. In the Salkowsky-Hesse test 0.002-0.003 gm. of 
the resin is placed in 3 cc. of chloroform and shaken with 3 cc. of 
concentrated sulphuric acid. The chloroform solution is then 
evaporated in a porcelain dish and the color of the residue noted. 
The color differs for various known resenes, from orange through 
lavender to blue, but is always a constant index for a particular 
resene. Substances that are not resenes do not give such color 
tests. In the Mach tests 0.003 gm. of the resin is placed in 1 Cc. 
