PREPARATION AND STAINING OF WOOD SECTIONS. 163 
will be much facilitated by placing the sections, after removal from 
the bleaching liquid, in a solution of hyposulphite of soda (1 
drachm to 4 oz. of water) for an hour,” then washing the sections 
by soaking them for at least six or eight hours in water, changing 
occasionally, and finishing with distilled water. If they are not to 
be stained at once, they should be preserved in water containing 
twenty per cent. of alcohol. If kept in water only, I find that 
in the course of two or three days they become covered with a 
peculiar fungoid growth. At this stage all air bubbles should be 
removed from the tissue. ‘This is conveniently done by placing 
the sections in dilute alcohol, putting them under the receiver of 
an air-pump, and exhausting the latter, repeating the pumping 
occasionally as long as air bubbles are given off. For this purpose 
I employ a small tube bottle, about 13 inches long, and a receiver 
just large enough to hold it, the process is thus rendered a rapid 
one. 
Where it is required to uniformly stain the section in order to 
render prominent the more delicate cell walls, logwood answers ex- 
ceedingly well and is very permanent. 
LoGwooD SOLUTION. 
Take of Logwood in coarse powder...............++ B07; 
DISHMIER. WALEr <tc nccsccuiees sas etenncaeeee eee 10 02. 
Boil for half an hour in a glass beaker, replacing what is lost by 
evaporation ; strain, and to each ounce of liquid, when cold, add 
sixty grains of alum and one drachm of alcohol, rub well together, 
filter through paper, and preserve in a stoppered bottle. 
STAINING ProceEss.—Make a filtering cone by twice folding a 
piece of filtering paper about 14 inches diameter ; support this in 
the neck of a small beaker or tube, and filter through it about ten 
drops of the above liquid, add thirty drops of distilled water, place 
the sections in the mixture for five (more or less) minutes, pour off 
the stain, wash once or twice in distilled water, then soak for half- 
an-hour in a solution of alum (twenty grains to the ounce), remove 
this, wash well with distilled water, and preserve in alcohol so as 
to be ready for mounting. 
The logwood solution prepared in this way gives more satis- 
factory results than when made as usually recommended from 
extract of logwood, the latter being a very variable article. Of 
double stains the most satisfactory are carmine and green and 
picro-carmine. The former method has been fully described in 
“Science Gossip” for January, 1880, and in recent numbers of 
this Journal. 
Picro-carmine is the most truly selective of any double stain I 
have yet employed. A special modification of it is required for 
wood sections as follows :— 
