Journal of Applied Microscopy. 275 



writer in his book. Gayet's paper gives unmistakable proof that his technique 

 was defective. He does not seem to have used the paraffine method at all, and 

 his stains were not suited to bringing out cell walls. His primitive methods and 

 his failure to read the book on Mosses and Ferns make Gayet's results rather 

 questionable where they differ from those of Prof. Campbell. c. j. c. 



Jordan, E. 0. The production of fluorescent ^" ^^'' publication there are presented 

 pigment by bacteria. Bot. Gaz. 27: 19-34, Some very interesting results bearing 



99- upon the production of fluorescence 



by bacteria.* In the experiment six cultures representing as many so-called 

 " species," were grown in various nutrient solutions of chemical compounds, the 

 molecular composition and arrangement of which were accurately known. When 

 in these solutions no sulphates were present, no fluorescence could be 

 obtained ; but when sulphates were present in sufficient quantity, fluorescence 

 appeared. The quantity of sulphate required is extremely small, 0.00001 per 

 cent, in the case of one of the cultures used being sufficient, while 0.0001 per 

 cent, sulphate resulted in the development of good fluorescence by five of the six 

 species. It seems quite likely that those who have reported fluorescence in the 

 abscence of sulphate have used commercially prepared nutrient solutions, which 

 frequently contain sulphates, although they may be marked " C. P." This was 

 probably true with Thumm's experiment. 



The base associated with the sulphate does not seem materially to affect the 

 production of pigment. In greatly concentrated solutions of nutrient substances 

 fluorescence is not so bright nor so persistent as in simpler solutions. Cultures 

 kept in the dark fluoresce more readily than those constantly in diffuse light. 

 The presence of an acid serves not only to neutralize the pigment already pro- 

 duced, but inhibits further development of pigment. The production of these 

 pigments is probably not worked out in order to assist the bacteria in obtainino- 

 proper nourishment, but rather they probably represent some of the products 

 which accompany the metabolic processes of these organisms. When certain 

 nutrient substances are present these pigments may be so formed. When other 

 nutrient media are present, metabolic by-products are formed which do not 

 chance to be fluorescent. Otis W. Caldwell, Chicago. 



Nelson, B. E. Microscopical examination of Since the trade in spices and condi- 



tea, coffee, spices, and condiments. (Chem- ments has been drifting away from the 



ical Laboratory, Binghamton, N. Y. State j • i 



Hospital.) Reprint from Merck's Report, druggist tO the grocer, adulteration 



1898. has been constantly increasing. The 



determination of the purity of these articles by chemical analysis is tedious and 

 often unsatisfactory, but the microscope furnishes a ready means of examination. 

 It is necessary, in the first place, to become familiar with the histological charac- 

 ters of teas, coffees, spices, etc. This paper gives numerous figures illustrating 

 histological characters, together with descriptions and directions for preparing 

 the material for microscopic examination. The articles figured and described 

 are tea, coffee, pepper, capsicum, caraway, ginger, mustard, cassia buds, cinna- 

 mon, cloves, allspice, mace, and nutmeg. c. j. c. 



*Beitrage zur Biologie der fluorescierenden Bakterien. Arb. d. Bakteriol. last. d. grossh. 

 Hochschule zu Karlsruhe, 1895. 



