126 BOTANICAL MICROTECHNIQUE. 



once. This reaction has been used by Rosoll (I, 17) for the 

 microchemical recognition of strychnine. He placed thin 

 sections from the seeds of Strychnos nux-vomica first in con- 

 centrated sulphuric acid, and observed that the contents of 

 the endosperm-cells become plainly rose-red from the pres- 

 ence of proteids and sugar (cf. 227), except the oil-drops,, 

 which remained uncolored. If now a small fragment of 

 potassium bichromate be added, the previously colorless oil- 

 drops take a beautiful violet color. Rosoll concludes from 

 this that the strychnine is dissolved in the oil-drops. 



Lindt (II) used a solution of an excess of eerie sulphate in 

 concentrated sulphuric acid for the recognition of strych- 

 nine. In spite of the gradual reddening of the eerie oxide, 

 this reagent remains fit for use a long time. Before its 

 use the sections should be treated with petroleum-ether 

 and alcohol for the removal of fatty oils, grape-sugar, and 

 brucine. If the solution be then added to the sections, all 

 the cell-walls become at once colored more or less strongly 

 violet-blue, while the contents of the cells at first remain 

 colorless. But after some time the reaction is disturbed by 

 various circumstances. Lindt concludes from this observa- 

 tion that the strychnine is contained in the cell-walls. But 

 Rosoll (I, 1 8) expresses the opinion that, during the extrac- 

 tion with petroleum-ether, the strychnine, formerly dissolved 

 in the fatty oil, is removed with it and becomes partly 

 diffused into the cell-walls. 



m. Theobromine, Dime tJiyl-x ant 1iin, C,H 8 N 4 O 2 . 



220. The alkaloid contained in the cocoa-bean, theobro- 

 mine, is best recognized, according to Molisch (I, 23), by 

 means of gold chloride, by adding to sections upon a slide, 

 first a drop of concentrated hydrochloric acid and then, 

 after about a minute, a drop of a $% solution of gold chlo- 

 ride. As soon as a part of the fluid has evaporated, long 

 yellow needles are formed at the edge of the drop, and 

 finally unite into feathery or tufted groups. The crystals 



