15 HAKUEM.\(i Ad'EXTS. 



used with equal success. Not more than 24 hours is necessary 

 for dehydrating and hardening nearly all kinds of plant tissue. 



The apparatus does away with the transferring of the tissues 

 from bottles containing alcohol of different strengths, and since no 

 such sudden transition occurs, the tissue is less liable to shrink. 

 Many different materials may be used for a diaphragm and almost 

 any speed of dehydrating can be obtained. The apparatus can be 

 made in any size to adapt it for private or general laboratory work. 



Picric Acid. 



This is to be recommended as a hardening agent. It acts 

 rapidly and energetically and should be used first in dilute solu- 

 tions. About one-fifth per cent, is the proper strength. Tissue 

 hardened in picric acid can be kept in 75 per cent, alcohol until 

 needed. If a little glycerin is added to the hardening agent, the 

 tissue will be less brittle. 



Chromic Acid. 



This agent can be used for hardening and with it the tissue 

 requires the same treatment as with picric acid. 



Osmic Acid. 



This acid is very useful as a fixing agent and is often used for 

 hardening. The tissue must not be kept in it long, as it will 

 become blackened and brittle. 



Hardening; Fluid. See p. 17. 



Other hardening agents are strongly recommended, but enough 

 has been said to enable one to properly prepare tissue for such 

 studies as may follow in this work. 



