200 The Botanical Gazette. [April, 
solution of gum arabic! and frozen at once. Tissues sectioned 
in this way are practically unaltered. Delicate tissues and 
those containing large air cavities can be sectioned with the 
greatest ease. The damage wrought in many tissues by de- 
hydration are entirely obviated by the freezing method. 
Frozen sections may be mounted in glycerin jelly or any 
aqueous medium. If mounted in glycerin, it will be found 
convenient to ring the cover with a thick solution of gum 
arabic. A glycerin-gum is then formed around the edge of 
the cover and in a short time is dry and hard on the outside. 
A ring of Canada balsam or cement may then be applied and 
the mount is as permanent as it is possible to make a glycerin 
mount. Frozen sections may be fixed to the slide for stain- 
ing purposes by Fol’s method (see Lee; Microtomist's Vade- 
Mecum, 218, 1893). 
When delicate parts are present, such as spores, etc., which 
are apt to fall out of the section, the following method can 
be used with entire success. 
A gelatin solution is made as follows: The best gold label 
gelatin is selected and carefully brushed clean and made Up 
according to the following formula: gelatin, 32 parts; distilled 
water, 48 parts; carbolic acid, 1 part. Dissolve the gelatin 
in a closed vessel over a water bath; add the carbolic acid and 
mix until it is thoroughly dissolved, and then add the white 
of one egg to clarify. 2 
The object to be cut is placed for a short time in the melted 
gelatin and quickly washed in warm water (about 90° Fah.) 
to remove the gelatin from the outside. It is then placed at 
once in water at room temperature. This sets the gelatin 
with which the object is now infiltrated, and the latter may 
be sectioned at once in gum arabic or preserved in two ie 
cent. formalin until needed. If sections cut in this way 4 
placed ona slide and a little glycerin added over a watt! 
* As some of the preservativ inari ic at 
. nea es ordinarily added to gum arabic 4! 
ee formalin is recommended for ohpaelhoony i L 
or this formula I am indebted to Mr. N, N. Mason of Providenc®, R. 
