BRIPFPOER AKTICLES 
THE STAINING OF WOOD FIBERS FOR PERMANENT 
MICROSCOPIC MOUNTS 
In the preparation of wood fibers for permanent microscope mounts 
there is some difficulty in fixing a deep enough color, especially in the 
vessels of the hardwoods, when simple solutions of aniline dyes, such as 
‘safranin, are used; and the method of using such a reagent as Haiden- 
hain’s haematoxylin involves much time and loss of some elements due 
to washing. To avoid these difficulties a saturated solution of nigroah 
in picric acid may be employed. 
To macerate the fibers the original green or dry wood is soaked in 
a mixture of 5 per cent nitric and 5 per cent chromic acids in equal parts, 
with heating to about 70° C. if there is little time. A somewhat stronger 
solution may be used cold, and in practice has resulted in sufficient 
maceration in the course of one or more days, depending largely upon the 
kind of wood being treated. It is not necessary to macerate the com- 
plete piece of wood, as radial slices may be removed and the fibers care- 
fully separated out with needles long before complete maceration is 
accomplished. After washing once in distilled water, the fibers are 
immediately put into the stain. To prepare the stain, saturate distilled 
water with picric acid and then saturate the solution of picric acid with 
nigrosin, and in applying to the fibers use a 25 per cent solution of the 
stain in distilled water. Fibers prepared according to this method are 
sufficiently stained, almost immediately, to a very fine light blue, which 
becomes darker until a deep blue-black is reached as they remain longer 
in the stain. In case the fibers do not take up the color, which seldom 
happens in the case of wood fibers, but is often the case in certain textile 
fibers, a stronger solution may be used. Even with the full strength, 
certain textile fibers, apparently those like cotton which contains no 
lignin, will not stain after a prolonged treatment. After staining, the 
material may be dehydrated and mounted in balsam in the usual manner. 
Benzol balsam is the kind we have employed, although there appears to 
be no reason why xylol balsam should not be used. The color will not 
hold in glycerin jelly mounts. In case a precipitate appears it may be 
Botanical Gazette, vol. 62] [318 
