40 BOTANICAL MICROTECHNIQUE. 



the method just described, after they have fully dried, with 

 the above-mentioned collodion solution (cf. 50) and letting 

 them dry in the air. I have used this method often recently, 

 and can recommend it heartily for difficult cases. It unites 

 the advantages of both methods in that it makes possible 

 the recovery of collapsed sections and permits the use of 

 aqueous stains without fear of separation of the sections. 



D. ATTACHMENT WITH ALBUMEN. 



52. According to P. Mayer's (I, II) methods, a solution of 

 albumen is used for attaching sections. This is prepared 

 by mixing 50 cc. of the albumen of hens' eggs with 50 cc. 

 of glycerine and I gram of sodium salicylate, and filtering 

 the mixture after hard shaking. A small drop of this solu- 

 tion, which, according to Vosseler (I, 457), becomes useless 

 in about six months, is placed on a carefully cleaned slide 

 and is rubbed with the finger or a soft cloth until a barely 

 visible film remains upon the slide. The sections are placed 

 upon this and pressed down upon the slide, a dry brush 

 being held between the finger and the sections. If the 

 slide is now heated over a small flame until the parafHne 

 melts, the sections become so firmly attached by the coagu- 

 lation of the albumen that the paraffine can be dissolved 

 out with xylol or other solvent without fear of their being 

 washed away. Nor does this occur when they are trans- 

 ferred directly from xylol to alcohol or from alcohol to 

 water. Neither have I observed the staining of the albu- 

 men film by any coloring matter ; so that this method may 

 be most conveniently used for most cases. 



IX. Making Permanent Preparations. 



53. One may use very various methods for preserving 

 preparations as long as possible. In nearly all cases prepa- 

 rations enclosed in Canada balsam or some other resin or 

 balsam possess the greatest permanence. But, on account 

 of their high refractive index, which nearly corresponds 



