1896.] MICROSCOPICAL JOURNAL. 251 



known, and the better the specimens are preserved, the 

 more valuable the collection. A very important, if not the 

 most important, question is, how to preserve the natural 

 color of the foliag-e as well as the color of the petals. 



No doubt, the rapidity with which the plant is dried 

 greatly influences the preservation of the natural color; 

 but in the course of time the g-reat majority will fade, 

 while others acquire different shades, some turn black, 

 some brown and various other colors. This last chang-e 

 of color frequently takes place while the plaiit is being- 

 dried, and more rarely later on. 



Not only the leaves, but the petals of most flowers change 

 in the same way, thus lowering the value of the specimen 

 to a considerable extent. 



Nienhaus published in the Schweizerische Wochenschrift 

 fur Chemie und Pharmacie his experience with oxalic acid 

 as a preserving agent of the color of petals of dried plants. 

 His theory was that ammonia in the air caused the fading- 

 of the color, and that it would be neutralized by this acid; 

 therefore, he recommended that the plant be dried 

 between filter-paper, which had previously been saturated 

 in a 1-per-cent solution of the chemical and then dried. 

 Nienhaus experimented with the petals of papaver rhoeas, 

 and was very successful. According to some American 

 writers, who have repeated his experiments, the results 

 were entirely negative. 



Since then I have had occasion to study the value of Nien- 

 haus' process, and have found that not only the petals are 

 well preserved, but that a 3-per-cent solution will also 

 preserve the color of the leaves. In the hope that the 

 results may be of interest to collectors of plants, I think 

 it proper to bring it to their notice. 



Several specimens, which had been dried by the aid of 

 1-per-cent. oxalic acid, did not give me as good results as I 

 had hoped to obtain, and I then determined to study the 

 value of different strengths of the solution, and find out 

 which would be most suitable to be employed in averag-e 

 cases. For this purpose I saturated some gray felt paper 



