252 THE AMERICAN MONTHLY [July 



with solution of oxalic acid, varying- in streng-ths from 1 to 

 5 per cent, and dried. 



Leaves of different texture were selected, dried be- 

 tween the thus prepared paper at ordinary temperature, 

 chang-ing- paper once in twenty-four hour. 



Leaves of a thin texture were well preserved with a 

 2-per cent solution ; not so well with that of 1 per cent. 

 Those dried between 3 to 5 per cent paper did not differ 

 materially in appearance from those dried with that of 2- 

 per cent strength. 



Leaves of a thick texture were best preserved with 3 per 

 cent of the acid, although the 4 and 5 per cent solutions 

 showed no disadvantage. 



The leaves of aquatic plants were best preserved with 

 2 or 3 per cent of acid ; the 1-per cent specimens turned 

 dark, and with 4 or 5 per cent they were almost black in 

 one case, while in other aquatics I could observe no differ- 

 ence between any of the specimens ; they all had kept 

 well. 



These results suggested to me that paper saturated 

 with a 3-per-cent solution of oxalic acid might be used 

 with more advantage for the majority of plants than a 1- 

 per-cent solution, as recommended by Nienhaus. It is not 

 unlikely that the kind of drying-paper used influences the 

 results to some extent. Nienhaus recommended filter- 

 paper to be employed ; in fact, the heavy felt paper mostly 

 employed in this country is not often used in Germany for 

 drying purposes; the botanists there prefer a very much 

 thinner gray paper. 



In almost all cases where a 3-per-cent solution of oxalic 

 acid was employed, I have obtained satisfactory and en- 

 couraging results, except with some members of the um- 

 belliferse, which turned dark when thus treated. I had not 

 the opportunity of making further experiments with them, 

 and do not know their behavior when dried in paper with- 

 out the aid of oxalic acid. The leaves of phytolacca decan- 

 dra, under ordinary circumstances, turned to a very dark 

 color; when dried by the aid of a 3-per-cent solution of 



