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 

 g-reatly 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 plant is being- 

 dried, and more rarely later on. 



Not only the leaves, but the petals of most flowers chang-e 

 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 

 w ere entirely neg-ative. 



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 g-ood results as I 

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

 value of different streng-ths 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 



