ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 281 



and 60 N violet on the contrary, notwithstanding their great colouring 

 power, did not exhibit any selective action with the nuclei. 



As to the greater or less resistance which very closely allied 

 species oppose to the action of the same reagent, the author mentions 

 that he has found small species of Paramecium continue to live in- 

 definitely without staining, whilst all the others of equal or greater 

 size had entirely disappeared from the same liquid. 



The staining of the nucleus of the Infusoria is, the author 

 (erroneously) says, " a new fact, and it is so much the more interesting 

 to note that the most recent researches demonstrate the prepon- 

 derating part which the nucleus plays in the phenomena of nutrition 

 and reproduction, and, if one may so say, in the government of the 

 life of unicellular organisms." 



Aniline Dyes and Vegetable Tissues.* — Mr. J. M, Macfarlane, in 

 a paper on the action of some aniline dyes on vegetable tissues, records 

 some of the more important methods arrived at. 



" Staining of Laticiferous Vessels. — Every botanist must have ex- 

 perienced the difficulty of obtaining thoroughly good preparations of 

 laticiferous vessels. Sachs recommends boiling in dilute potash ; but, 

 while tolerably good sections may be obtained in this way, several 

 difficulties are encountered. The points to be aimed at in preparing 

 this tissue are (a) the coagulation of the latex, so that it may continue 

 to fill the vessels ; (&) the staining of the cut sections, so that the 

 vessels may be distinctly differentiated from the surrounding cellular 

 substance ; (c) the successful mounting of these, so that the tint may 

 be permanently retained. The first part of the process is best accom- 

 plished by obtaining, for example, a large and entire root of Scorzonera, 

 so that extensive bleeding may be prevented. A suitable sized bottle 

 being filled with alcohol, pieces of the root from one to two inches in 

 length are cut and immediately placed in it. Coagulation of the 

 latex is quickly effected. After lying thus for a week or longer, 

 sections are cut with the hand, or by aid of a microtome. The second 

 point is most important, and on its success the beauty of the object 

 will depend. The sections are placed in alcoholic solution of saf- 

 franine, obtained by dissolving 1 part of this dye in 800 parts 

 spirit. After 18 to 24 hours, they are removed from the stain and 

 decolorized by washing repeatedly in spirit. It will be found that 

 the stain leaves the cellular tissues rapidly, while it is retained by 

 the latex in the vessels. We will notice, lastly, the best method for 

 mounting these. While such media as balsam or dammar would 

 cause unnatural contraction, fluids, on the other hand — especially 

 acetic acid solution — are apt to act slightly on the dye. I have 

 found nothing to equal glycerine jelly, as it preserves the tint and is 

 easily worked. 



Double Staining of Stems, &c. — The dyes usually recommended for 

 this purpose are rosaniline and iodine green ; but saffranine and 

 emeraldine are preferable, as the former is, for vegetable tissues, a 



* Trans. Bot. Soc. Edin., xiv. (1881) pp. 190-1. 



