ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 839 



The basic aniline colours to be specially recommended are Bismarck- 

 brown, methyl-violet, methyl-green, saffranin, fuchsin, and magdala, 

 and gentian-violet most of all, employed as a 1 per cent, aqueous 

 solution. In this the section is laid, and soon becomes diffused with 

 blue, and is then placed for an hour or more in alcohol, and finally 

 in water, alcohol, or oil of cloves. The most important condition is 

 that the section be well hardened. In preparations coloured by 

 gentian- violet the nucleus can then be coloured red by carmine, 

 Partsch's alum-cochiaeal, Grenacher's alum-carmine, borax-carmine, 

 or picrocarmine. 



The following method is given for the manufacture of picro- 

 carmine as a micro-chemical reagent : — 2 gr. of carmine are immersed 

 in 4 gr. of ordinary ammonia, and placed for 24 hours in a spot 

 protected from evaporation, and then shaken up with 200 gr. concen- 

 trated solution of picric acid. After allowing to stand again for 

 24 hours, everything soluble is dissolved. Very small quantities of 

 acetic acid are then added, until the first slight precipitate apj)ears ; 

 and after the lapse again of 24 hours, a few drops of ammonia are 

 added. 



Colouring of Suberized Membranes by Fuchsin.* — M, Olivier 

 gives the following process for colouring suberized membranes : — 

 the sections of the roots are treated with a solution of fuchsin, made 

 with equal parts water and alcohol, by which the whole preparation 

 is coloured. The sections are then steeped in absolute alcohol, which 

 dissolves the fuchsin out of the membranes, which are composed of 

 cellulose, whilst the suberized walls remain of a red colour. 



Nigrosine for Colouring Nuclei of Vegetable CeUs.j — M. Errera 

 finds "nigrosine" an excellent reagent for the nuclei, which are 

 coloured a very deep blue, and stand out very clearly, the rest of the 

 cell remaining practically colourless. 



Nigrosine is one of the derivatives of tar, and belongs to the class 

 of indulines. It is soluble in water and insoluble in alcohol and 

 ether, and for colouring should rank with safranine, methyl-green, 

 and other recognized agents. 



The preparation should be placed for a short time in a solution of 

 nigrosine, and then washed in distilled water until the water takes up 

 no more colouring matter. It can then be mounted in glycerine or 

 in balsam or dammar. The former method is preferable if it is 

 desired to study the protoplasm and the part of the nucleus formed by 

 achromatine (of Flemming). The second should be adopted for the 

 examination of chromatine (= nucleine), as the grains of starch 

 which hinder observation are rendered invisible. 



Staining Nuclei.^ — H. Grenacher uses for discovering the nuclei 

 in organs which abound in pigment — viz. the eyes of spiders — a 

 method which will probably be found useful in other cases, especially 



* Bull. Soc. Bot. France, xxvii. (1880) pp. 234-5. 

 t Bull. Soc. Belg. Micr., vii. (1881) pp. exxxiv.-v. 



i Unters. u. d. Sehoigan d. Anthropoden, 1879, p. 24. Cf. Zool. Jabresber., i. 

 (1880) p. 38. 



