1913-14.] BOTANICAL SOCIETY OF EDINBURGH 237 



wax. It is desirable, prior to inserting the wax cylinder 

 into the well of the microtome, to make a shallow longi- 

 tudinal groove in the wax so as to allow the escape of air 

 as the embedded material is pushed in. A further pre- 

 caution is necessary with this form of microtome. The 

 wax round the upper end of the material should be care- 

 fully removed with a sharp knife, at least from the near 

 side {i.e. the side which first confronts the razor) of the 

 block. In order to secure good resistance to the razor, the 

 wax on the far side can be advantageously left intact. 

 Other forms of cheap microtomes requiring only the 

 clamping of the wood cubes in position can also be 

 effectively used. 



The sections are first placed in strong alcohol in a 

 watchglass. which is then held, by means of a pair of 

 forceps, over the naked flame of a small spirit lamp until 

 the alcohol nearly reaches its boiling point. The air in the 

 section is by this treatment entirely and quickly expelled. 

 Much time is saved by the heating, while the hot alcohol 

 also often removes much of the colouring matter and other 

 substances from the tissues. The sections are then trans- 

 ferred to a watchglass containing pure lactic acid, and held, 

 as before, over a naked flame until bubbles begin to form 

 in the liquid, when the watchglass and contents are 

 removed. Lactic acid, though very seldom used, is a 

 valuable reagent, and, besides having the effect of clearing 

 the sections somewhat, it improves their condition after 

 treatment with strong alcohol. Should the timber be 

 very highly coloured it may, perhaps, be necessary to use 

 some other clearing reagent at the outset, although it 

 may be added that even in such cases alcohol and lactic 

 acid generally suffice. 



Staining. — The sections are, after treatment with the 

 acid, transferred to a watchglass containing carbolic fuchsin 

 (Ziehl's formula. See Lee s " Microtomist's Vade-Mecum "), 

 where they remain only for a short time. This stain is 

 one of the simplest to use, and one of the most efficient for 

 the purpose of photography. The best strength of fuchsin 

 will be readily ascertained by a few trials. If necessary, 

 add a little dilute alcohol. The sections when stained 

 sufficiently require two or three successive washings in 



