THE AMERICAN BOTANIST 69 



according to the size, although 71 hours was abundant for 

 most specimens to completely assume the color of the reagent, 

 when they may be removed and washed. Six to twelve hours 

 of the latter usually removed most of the stain of the chromic 

 acid, leaving a color easily as desirable as that secured by or- 

 dinary methods of preparation. The chemically treated speci- 

 mens after drying and pressing were ready in most cases for 

 mounting at least three days ahead of the controls, and show- 

 ed no tendency to mould in the moist climate at the Labora- 

 tory. Specimens of the cactus acquire a leathery consistency 

 and an olive green color. This killing fluid and the following 

 may be used at least three times without impairing their 

 powers for this purpose. 



Porv.ialin- Acetic Solution. (Basic formula: 100 cc. 4% 

 formalin; 3cc. glacial acetic acid.) Under similar conditions 

 to those governing the use of the medium chromo-acetic solu- 

 tion, similarly satisfying results were obtained by the use of 

 formalin acetic solution. Penetration was more rapid, and 

 the period of washing is safely abbreviated. The treated 

 specimens exhabited a somew^hat pale color, and with pro- 

 longed exposure to the reagent became somewhat fragile and 

 brittle. 



Denatured Alcohol. (This was 95% alcohol apparent- 

 ly containing formalin.) After 24-43 hours treatmentwith this 

 fluid, followed by 3-4 hours washing, small specimens of all the 

 l)lants with the excepticMi of /Irenaria w^ere ready for pressing 

 and drving. In the case of ^^rf;wn«, the brittle (|uality of the 

 leaves was best overcome by the use of the other killing fluids. 

 Specimens treated with alcohol were of a paler color than 

 those treated with other chemicals, althought there was not 

 any great appreciable difference in the cases of Sueda and 



