166 SUMMARY OF CURRENT RESEARCHES RELATING TO 



serviceable in detecting coniferin. Water is added to a 20 per cent, 

 solution of thymol in absolute alcohol as long as it remains clear and 

 no thymol is precipitated. Crystals of potassium chlorate are then added 

 in excess, and the solution is allowed to stand several hours, and filtered. 

 Some paper which contained only a trace of coniferin was taken and 

 moistened with this liquid, and a drop of concentrated hydrochloric acid 

 added ; in a few minutes, although in complete darkness, the moistened 

 part became bluish green. With this reagent, sections from the stem of 

 over a hundred woody and herbaceous plants were tried, and always with a 

 positive result. In all the sections the lignified portions only became blue ; 

 in the first place the walls of the xylem-elements, then those of the pith 

 and the bast-cells. 



Finally, the author refers to a paper of Wiesner's, who states that he 

 obtained a red-violet colour when phloroglucin, lignin, and hydrochloric 

 acid are brought together. The presence of phloroglucin in some measure 

 conceals the reaction for coniferin ; but not so much so as to make it 

 altogether inapplicable. 



Engelmann's Bacterium-inetliod.* — Dr. N. Pringsheim replies to 

 Engelmann's further defence "j" of the accuracy of this method of deter- 

 mining the intensity of the evolution of oxygen in plants under the 

 influence of sunlight. He reasserts the inadequacy of the method of 

 successive observations, from the inconstancy of the minimum width of 

 the cleft needful for the movement of the bacteria in the different colours. 

 The movement can often be followed up to the disappearance of the object, 

 and it usually ceases in all colours at nearly the same width of cleft, which, 

 in direct sunlight, is about O'OOS mm.; while, on the other hand, the 

 minimum widths for the visibility of the movement in the different colours 

 of the spectrum — red, yellow, green, and blue— do not stand in a constant 

 relationship to one another, as required by Engelmann's theory. 



Preparing the Bacillus of Lustgarten.| — MM. Alvarez and Tavel have 

 modified Lustgarten's method as follows: instead of sulphui'ic acid they 

 use 2 per cent, oxalic acid ; a stay of two hours in the warm solution they 

 find sufficient ; and they double stain with eosin, picro- carmine, and 

 safranin. They approve De Giacomi's method if the iron chloride be 

 strongly acid. Against Lustgarten they maintain that the syphilis bacillus, 

 like that of tubercle, strongly resists decolorization by acids (33 per cent, 

 nitric, hydrochloric and sulphuric acids). The authors, however, mention 

 a difference between the two bacilli, which is, that Lustgarten's microbe 

 becomes immediately unstained by alcohol after treatment with acid : the 

 acid must therefore be well washed out in water, if the colour is to be 

 retained. 



Method of obtaining Uric Acid Crystals from the MalpigMan Tubes 

 of Insects, and from the Nephridium of Pulmonate Mollusca.§ — By the 

 method adopted by Dr. C. A. MacMunn, he obtained abundance of crystals 

 of uric acid from the contents of the Malpighian tubes of a single insect, and 

 the method is therefore likely to be useful in determining whether a given 

 organ in an invertebrate animal discharges a renal function or not. 



The insect examined was Pe.riplaneta orientalis. The Malpighian tubes, 

 after crushing, were boiled in distilled water to dissolve the supposed 



* SB. Versamml. Deutsch. Naturf. u. Aerzte, Sept. 20, 1886. See Bot. Cen- 

 tralbl., xxviii. (188G) p. 93. 



t See this Journal, 1886, p. 705. J Arch, de Physiol., xvii. (1885) p. 303. 



§ Journ. of Plivsiol., vii. (1886) pp. 128-9. 



