ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
241 
ment with picric acid may be followed by more severe swelling by means 
of zinc chloride or sulphuric acid. 
With regard to staining, it is possible, in certain special cases, to 
stain the connecting protoplasmic threads either with safranin alone, or 
by introducing safranin by means of a somewhat intricate substitution 
method, the sequence being Hofmann’s blue (or soluble water-blue), 
raethylen-blue, safranin. The safranin may then be succeeded by gentian- 
violet or by eosin ; with gentian-violet Gram’s method is the best. In 
all cases the staining is practically limited to the protoplasmic threads. 
But with ordinary tissues this method is not applicable ; since the 
whole of the wall becomes deeply stained, and the threads are no longer 
visible. To avoid this, the method was adopted of staining and washing 
out, using for the purpose orange G or acid fuchsin. With ordinary 
tissue the staining appears to be more easily accomplished than with 
the thick mucilaginous walls of endosperm-cells. Excellent results 
may be obtained by staining at once with safranin and washing out with 
orange G. This may be followed by staining with gentian-violet, suc- 
ceeded by treatment with acid fuchsin, or the sequence of staining 
may be safranin, gentian-violet, acid fuchsin. Substitutions in which 
safranin, gentian- violet, and eosin are included give good results. 
Use of Permanganate in Microtechnique.* — M. M. Tswett finds 
potassium permanganate a useful reagent for causing swelling of the 
protoplasmic structures, and thus assisting in the observation of the 
structure of the chromatophores. The same reagent may also be 
employed as a macerating substance ; beautiful preparations were thus 
obtained of the sieve-tubes of Vitis. 
Preparation of Pigments for Depicting Microscopical Prepara- 
tions. | — Herr W. Baklanoff rubs up anilin pigments in a mortar with 
strong gum arabic solution until the mixture is of the consistency of 
paste. Glycerin in the proportion of 1 drop to 1 ccm. of the mixture 
is then added. The paste is then incubated at 37-38° until hard. In 
this way pigment-masses are made which, when used for depicting micro- 
scopical preparations, reproduce the original colours very faithfully. 
Pigments made in this way form masses which are compact, homo- 
geneous, and do not run or soak through the paper. Haematoxylin may 
be prepared in a similar w r ay. 
Visibility and Appearance of Unstained Centrosomes.f — Prof. E. 
Ballowitz maintains that centrosomes are more easily examined and 
clearly seen in the unstained condition when merely fixed with Flem- 
ming’s solution than when treated with sublimate and specific stains. 
Clearing Vegetable Sections. § — Mr. W. Kirkby recommends the 
following procedure for treating sections of vegetable tisssue, as it leaves 
the sections in a condition suitable for mounting in liquid, gelatinous, 
or resinous media : — Place the sections in a fresh clear solution of 
chlorinated lime until they are quite bleached (2.-5 minutes). Warm 
gently in a test-tube for a few seconds, then quickly replace the solu- 
* Bull. Lab. Bot. Univ. Geneve, i. (1897) pp. 13-5. 
t Zeitschr. f wiss. Mikr., xiv. (1897) pp. 366-8. 
X Tom. cit., pp. 355-9. § The Microscope, v. (1897) pp. 151-2. 
