ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 695 



Laboratory Notes. 



[Preserving a specimen temporarily by applying a drop of glycerin at the side of 

 the cover-glass iu such a manner as to effect a union between the water and the 

 glycerin ; value of dried specimens of algae, &c.] 



Amer. ^':tural., XXI. (1887) pp. 477-9. 



TRZEBiysKi, St. — Einiges iiber die Einwirknng der HartTingsmethoden anf die 



Beschaffenheit der Oanglienzellen im Btickenmark der Eaninchen und Hunde. (On 



the influence of hardening methods on the condition of the ganglion-cells in the 



spinal cord of rabbits and dogs.) Virchow's Arch. f. Path. Anat., CVII. (1887) p. 1. 



Williams, C. F. W, T. — Mounting in Castor Oil. 



[Cell to be made with Ward's brown cement and filled with best castor oil. '• For 

 plant crystals, such as laphides and the like, there is no preservative so good in 

 my opinion as this oil." 



Scl.-Gosslp, 1887, p. 138. 



(6) Miscellaneous. 



New Micro-chemical Reaction for Tannin.* — Experiments were made 

 by Herr J. W. Moll, for the purpose of discovering a good reagent for 

 tannin in the cells of plants, which should give a precipitate sharply sepa- 

 rated from the surrounding fluid, and at the same time should show clearly 

 the distinction between the tannins which colour iron green, and those which 

 colour it blue. He obtained the desired results with lithium chlorate, 

 copper acetate, copper nitrate, lead nitrate, and uranium acetate, the iron- 

 salt used being the acetate. Of these copper acetate answered the best. 



The living parts of plants to be examined were cut into small pieces 

 and left in a saturated solution (7 per cent.) of copper acetate for from eight 

 to ten days ; longer immersion produces no injurious results. The sections 

 were then placed on the slide in a drop of ' 5 per cent, iron acetate solu- 

 tion, but allowed to remain in it only for a few minutes, as longer action 

 colours the cell-walls brown. After washing with water, and then with 

 alcohol to remove the air and chlorophyll, they were examined in glycerin, 

 or glycerin jelly, in which they remain unaltered for a lengthened period, 

 even as much as two years. Or the sections may be removed directly from 

 the copper acetate into alcohol, and examined afterwards with the assistance 

 of iron acetate. The distinction between the tannins which give green and 

 blue colours with iron were very clearly brought out. Thus in branches of 

 Fagus the tannin-cells of the bark were coloured green, those of the pith blue. 



Micro-chemical Reactions based on the formation of Crystals.t — 

 MM. Klement and Renard have published an important paper on micro- 

 chemical reactions. The methods available for the qualitative analysis of 

 minute quantities of a substance are spectroscopic analysis, blow-pipe 

 analysis, and micro-chemical reactions. The last method depends on the 

 form and appearance of the crystals deposited by the action of reagents. 

 Availing themselves of the researches of Boricky, Behrens, Streng, Lehmann, 

 Haushofer, and others, combined with the results of their own extensive 

 researches, the authors have produced the most complete account of the 

 subject which has yet appeared. They describe the methods of research 

 and the reactions, simple and characteristic, by which compounds of more 

 than fifty elementary bodies may be identified in minute crystals recog- 

 nizable under the Microscope. They also give a brief description of the 

 processes of isolation and identification applicable to such compounds as 

 the mineral constituents of rocks. The value of the treatise is much 

 enhanced by the accompanying plates, eight in number, comprising nearly 

 100 figures of the forms of crystals obtained by the various reactions 

 described in the text. 



* Maandbl. voor Natuurwet., 1884. See Bot. Centralbl. xxiv. (1S85) p. 250. 

 t Cf. Bull. See. Belg. Micr., xii. (1886) pp. 11 and 5-5-6. 



