﻿252 BOTANICAL GAZETTE [march 



extent upon the composition of the fixing or killing reagent. Generally 

 the material is left in the pure chloroform 2 hours, or until it sinks to the 

 bottom of the vessel. Material such as root tips or lily anthers fixed 

 in chromo-osmic-acetic acid or chromo-osmic acid will sink in pure 

 chloroform within 2 or 2.5 hours, but if chromo-acetic acid, absolute 

 alcohol, or reagents that do not contain osmic acid are used as killing 

 reagents, the specimens sink slowly or not at all. In the case of material 

 fixed in chromo-acetic acid, for example, the specimens are left in the 

 pure chloroform overnight or longer if necessary. 



The specimens are now changed to a fresh quantity of pure chloro- 

 form, and shavings of paraffin (melting point 42-45 0 ) are added until at 

 room temperature no more paraffin will dissolve. It will be seen that 

 the paraffin floats at the surface of the fluid, while the specimens, in 

 case they have sunk, are at the bottom. The chloroform surrounding 

 the objects becomes gradually saturated, therefore, at room temperature. 

 If the objects have not sunk in the chloroform, they do so gradually as 

 the paraffin is dissolved. The degree of saturation of the solution may 

 be increased slowly by adding paraffin a little at a time, but the writer 

 has not found any special care necessary. When the chloroform is 

 saturated at room temperature, the vessel is placed upon the paraffin 

 oven and a little more paraffin is added if desired. The vessel, which is 

 still closed with a stopper, remains on the oven 2-1 2 hours. The contents 

 are now poured out into an open dish (usually a small porcelain dish) 

 and covered by only a slip of paper to keep out dust, and this dish 

 remains upon the oven until so much chloroform evaporates that the 

 paraffin congeals slightly at the edge of the dish or over the whole 

 surface. This requires usually one night. The dish is then placed inside 

 the oven and allowed to remain until all the chloroform has evaporated, 

 as determined by taste. The specimens are now transferred to melted 

 paraffin of 52-55 0 melting point, or that of a higher melting point if 

 necessary, in which they remain 10 minutes to 2 hours or longer before 

 imbedding. They are then imbedded in this or similar paraffin. 



Although chloroform is expensive, this is not necessarily a costly 

 process. The paraffin (45 0 melting point) used in making the chloroform- 

 paraffin solution may be used over again two or three times, and 8 cc. of 

 chloroform in each vessel is sufficient for a quantity equal to 10 or 15 root 

 tips of onion or lily anthers. 



It is understood, of course, that chloroform should be kept out of 

 direct sunlight, preferably in a dark place— D. M. Mother, Indiana 

 University, Bloomington, Ind. 



