5<D MICRO-CHEMICAL REAGENTS. 



Thiersch gives the following formula for its pre- 

 paration. One part of carmine is dissolved in one 

 part (by weight) of concentrated ammonia and 

 three parts of distilled water. This solution is 

 mixed with eight times its volume of dilute oxalic 

 acid (i : 22). Twelve volumes of absolute alcohol 

 are then added, and the whole is filtered. The 

 filtrate may be rendered more orange in color by 

 the addition of oxalic acid, or more violet by the 

 addition of ammonia. If oxalate of ammonium is 

 precipitated, it can be removed by filtration or redis- 

 solved by the addition of a few drops of ammonia. 



Grenacher's alum-carmine, recently introduced 

 into vegetable histology by Tangl, 1 is prepared by 

 him in the following manner. A saturated aqueous 

 solution of alum is made. The desired quantity 

 of carmine is dissolved in it, the solution is boiled 

 for about ten minutes, allowed to cool, and filtered. 

 Walls consisting of cellulose are colored bright-red 

 by this preparation, while those containing su- 

 berin or lignin remain unstained. Protoplasmic 

 bodies and the nuclei of cells are also stained with 

 difficulty, and but slightly. It is recommended 

 that parts of plants from which sections are to be 

 cut, shall be hardened in absolute alcohol, as this 

 increases the power of the membranes to take up 

 the coloring matter. 



1 Tangl . Ueber offene Communication zwischen den Zellen des Endo- 

 sperms. Jahrb.fiir wiss. Bot., 1880, XII., p. 170. Grenacher : Archiv. f. 

 mikr. Anatomie, 1879, p. 465 ; Zeitschrift f. Mikroskopie, 1879, Jahrg. 

 II, P . 55- 



