68 THE AMERICAN BOTANIST 



ed by botanists to be equal if not superior to those obtained 

 by the older methods. 



The experiments upon which this newer method rests 

 were made at the Biological Laboratory of the Brooklyn 

 institute of Arts and Sciences, Cold Spring Harbor, N. Y. dur- 

 ing the summer of 1921. The following species of succulent 

 plants were used, Opuntia vulgaris Mill, Salicornia europea 

 L.. Siieda niaritima L., Sediim purpnreum Tausch, Cakile ed- 

 entula Hook, and Arenaria peploides L. The starting point 

 was the study of the effect upon these plants of the more 

 common fixing and killing reagents known to the plant 

 histologist, with preference given to those more cheaply ob- 

 tained and more likely to be a reagent in the herbarium. To 

 facilitate the pentration of the reagents, incisions were made 

 at from 1-3 in. intervals along the stems or stem-like struc- 

 tures of what would eventually be the ventral surface of the 

 plant when finally mounted. In Opuntia, however openings 

 were made all around the edges of the separate phylloclades, 

 and the epidermis of one side of these punctured with a needle 

 at the point of attachment of the spines. Each specimen of 

 plant used was then immersed in a quantity of killing fluid 

 about five times its own volume, and weighted down if neces- 

 sary with a piece of glass. Controls for the experiments were 

 made by preparing other herbarium specimens in the ways 

 first indicated. The results of interest to the systematic bo- 

 tanist from the series of experiments are now present under 

 the headings of the reagents used. 



Medium Chr onto- Acetic Acid Solution. (Basic formula 

 as designated by Chamberlin : Chromic acid, .5 gm; glacial 

 acetic acid, .1 gm ; water, 100 cc. ) Well perforated speci- 

 mens of the above named plants were treated with this fluid 

 from 24-43 hours; in the of Opuntia, a longer time varying 



