ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
673 
above the level of the stage. A thermometer placed by the side of the 
preparation indicates the temperature of the latter. 
The most convenient temperature for observations ranges from 37°- 
38°, and if observations are to be maintained longer than eight or ten 
minutes it is necessary not only to add warm water, but to remove the 
surplus in order that the original level may be maintained. This can 
be effected as in the illustration by means of two siphons, or by placing 
the glass vessel within one which is larger but not so high. 
By means of this apparatus the author stales that he has made more 
observations in a month than in the past twenty years with the old 
arrangements. 
Microchemical Tests for Alkaloids and Proteids.* — M. L. Errera 
points out the want of a general test for the discrimination of alkaloids 
and proteinaceous substances. Although many alkaloids are readily 
detected by special reactions, yet Raspail’s proteid-reaction (a red 
colour produced by sugar and sulphuric acid), and Millon’s reaction, 
are both also produced by certain alkaloids. The best general 
distinctive tests for these two classes of substances are their different 
behaviour towards (a) absolute alcohol, ( b ) one gr. of tartaric acid 
in 20 ccm. of absolute alcohol, ( c ) 0*2 ccm. of hydrochloric acid in 
5 ccm. of distilled water and 95 ccm. of absolute alcohol. In these 
three reagents all alkaloids are readily soluble, while proteinaceous 
substances are either entirely insoluble, or at all events leave a residue 
behind, even after very long treatment. 
Reactions for Lignin.f — Herr R. Hegler discusses in great detail 
the various reagents used for the micro-chemical detection of lignified 
membranes. He divides those already in use into three groups, viz. : — 
(1) Those which react with vanillin, but not with coniferin, — thallin ; 
(2) Those which react with coniferin but not with vanillin, — phenol- 
hydrochloric acid, thymol-hydrochloric acid; (3) Those which react 
with both vanillin and coniferin, — all the other reagents for lignin. 
Thallin, C 9 H 6 NOCH 3 H 4 , is an extraordinarily delicate reagent for ligni- 
fied tissues, the vanillin assuming an intense orange-red colour. A 
new reagent recommended, with the same properties, is toluilendiamin, 
C 6 H 3 (CH 3 )(NH 2 ) 2 , used in a concentrated aqueous solution with a 
trace of hydrochloric acid ; it stains lignified membranes a dark 
orange. Vanillin he regards as a product formed out of coniferin by the 
activity of the protoplasm; the process being of the nature of fermen- 
tation with secondary oxidation. The production of lignin, C 18 H 24 O 10 , 
out of cellulose may be represented by some such equation as this: — 
4C 6 H 10 O 5 = C i8 H 24 O 10 + C 6 H c 0 5 + 5H a O; the C 6 H 6 0 6 may then be 
completely oxidized into carbon dioxide and water, or may pass over 
into such substances as tannins. 
Fixing and Staining of Leucoplasts and Protein-crystalloids.J — 
Dr. A. Zimmermann recommends a concentrated alcoholic solution of 
* ‘Sur la distinction microchimique d. alcaloides et d. raatieres proteiques,’ 
Bruxelles, 1889. See Bot. Ztg., xlviii. (1890) p. 232. 
f Flora, lxxiii. (1890) pp. 31-61 (1 pi ). Cf. this Journal, 1889, p. 606. 
X Beitr. z. Morph, u. Physiol, d. Pflanzt nzelle, Heft 1, 79 pp. and 2 pis., 
Tubingen, 18S0. Cf. supra , p. 617. 
