1890.] MICROSCOriCAL JOURNAL. 191 



or the tissue will come through very inucli shruukeu and distorted, 

 worthless biologically. 



I have had the most success following the method described by Dr. 

 J. W. Moll, in the Botanical Gazette for Januruy, tSS8. I have ob- 

 tained good sections from all the material that I have treated in this 

 way. I used a i per cent, solution of chromic acid and 20 per cent., 

 35 per cent., 50 per cent., 75 per cent., and 90 per cent, alcohols for 

 dehydrating. The chromic acid seems to fix the protoplasm, and ma- 

 cerate the cellulose, allowing the alcohols to pass more freely. 1 al- 

 lowed the specimens to remain in the several per cents, of alcohol from 

 two to twenty-four hours, according to their size and texture. As a 

 rule, I found that the more gradually the specimens were dehydrated 

 the better. From absolute alcohol, the specimens were placed in a so- 

 lution of equal parts turpentine and paraffine. The solution contain- 

 ing the specimens was then raised gradually from a temperature of 20° 

 -f- C. to about 45° C. They were then placed in melted paraffine, kept 

 as nearly at 50° C. as possible. Small specimens will be permeated in 

 one or two hours, but large specimens require from four to six hours. 



From the 75 percent, alcohol I placed the specimens in a stain. The 

 stains I tried were alum cochineal, hiematoxylin, fuchsin, methyl green, 

 methyl blue, methyl violet, and anmionia carmine. I found alum coch- 

 ineal a good stain for fungi, plumules, stems, roots, and root-tips, but 

 it would not penetrate the cucumber cotyledons. Fuchsin would pen- 

 etrate anything I tried ; but as it is soluble in alcohol it is necessary to 

 overstain the specimens, and then allow the coloring to come out until 

 it is about right. Htematoxylin stained all the tissue that I tried except 

 the young cucumber cotyledons. This stain gives large specimens a 

 dark blue color on the outside, and a purplish pink color on the inte- 

 rior. The nuclei and the cell walls are brought out clearly. I did not 

 have good success with the methyl colors, as they were easily dissolved 

 out by the alcohol. 



If specimens have not taken sufficient color, or if the alcohol has re- 

 moved too much of the color, sections can be stained upon the slide, 

 after they are cut. Any stain can be used, but none that I tried difler- 

 entiated the parts sufficiently. Fuchsin will give enough color in a few 

 seconds. The sections must stand in hsematoxylin from two to ten 

 minutes, and in alum cochineal from ten to twenty minutes. If it is 

 intended to stain upon the slide, an alum fixative will be found better 

 than collodion. 



I heated the slides in the gas-fiame to melt the paraffine, and poured 

 on turpentine to wash it out. The specimens were then mounted in 

 balsam dissolved in. chloroform. Air bubbles that appear when sec- 

 tions are first mounted, will disappear after the slides stand a few hours. 

 If the razor or knife used for cutting is very sharp, small specimens may 

 be cut 1-2500 or even 1-5000 of an inch in thickness. But larger speci- 

 mens cannot be cut more than 1-600 to i-i5ooof an inch thick without 

 crowding the tissues together, and giving them the appearance of being 

 shrunken. 



Correction. — The article in our last issue, by Dr. Whelpley, on 

 the use of the mircoscope in pharmacy, should have been credited to 



the Druggists' Circular. 



