I9 6 BOTANICAL MICROTECHNIQUE. 



under side of the slide is very hot to the touch. Boiling the 

 solution is to be avoided, though its complete drying up 

 does not injure the staining. When the solution has acted 

 from two to five minutes, or longer, it is rinsed off with a 

 mixture of one part alcoholic picric acid solution and two 

 parts water, and the washing with this solution is, in general,, 

 continued until the sections no longer give off any visible 

 color. But in many cases various degrees of staining may 

 be obtained by stopping the washing earlier or later. The 

 picric acid is finally removed with alcohol, and the prepara- 

 tion mounted in Canada balsam in the usual way. 



It may be observed that, according to Altmann's direc- 

 tions, the sections should be gently warmed again in picric 

 acid solution after being washed with it, in order to obtain 

 good differentiation. But with vegetable objects I have in. 

 most cases obtained no good results from this warming with 

 picric acid, while otherwise this method has repeatedly done 

 me good service. 



With this method a very deep staining of the nuclear crys- 

 talloids is always obtained ; but it is inferior to the two fol- 

 lowing methods in that, especially in young cells, at least 

 when fixed with sublimate, the nucleolus is also pretty deep- 

 ly stained. 



b. Acid Fuchsin Method B. 



346. The second method, which I have called " acid f uch- 

 sin method B" (cf. Zimmermann II, 14), is adapted as well 

 for free-hand sections as for those from the microtome. The 

 well-washed sections are placed first in a .2$ solution of acid 

 f uchsin in distilled water, to which a little camphor is added 

 to make it keep better. They remain in this solution at 

 least several hours, best 24 hours or longer.* They are then 

 washed as quickly as possible in running water (cf. 39). 

 The time necessary for this differs much in different cases, 

 and varies between a few minutes and several hours. But it 



* If many sections are to be stained at the same time in this way, the ves- 

 sel described in 37 may be used. 



