388 Introduction to Botany. 



To do this, place a drop of chloroiodide of zinc on the slip in contact 

 with the coverglass, and place a piece of filter paper in contact with 

 the opposite side of the coverglass. By this means the acid will be 

 drawn from under the coverglass and the chloroiodide of zinc will 

 occupy its place. 



Safranin. — Dissolve safranin to saturation in 95 % alcohol and dilute 

 with an equal bulk of distilled water. This is very useful in staining 

 sections of plant tissues, or for staining unicellular or filamentous Algae 

 or Fungi which have been fixed in chrom-acetic fixative (which see). 

 The material should lie in the stain over night, or even for 24 hours. It 

 should then be transferred to a small amount of 50% alcohol, and strong 

 alcohol added to this drop by drop until the color in the material has a 

 transparent quality, but is still quite evident. The material may now 

 be mounted in a drop of dilute glycerine under a coverglass for imme- 

 diate study with a microscope, or permanent mounts may be made in 

 glycerine jelly as follows : Transfer the material from the alcohol rins- 

 ing bath to equal parts of glycerine and water, and leave it in a place 

 free from dust until the glycerine has become concentrated by the evap- 

 oration of the water. Then mount it in glycerine jelly, as described 

 under that head. 



Staining Paraffin Sections, and Sealing in Balsam. — Having mounted 

 paraffin sections as directed under Cutting and Mounting Paraffin Sec- 

 tions, and having dissolved away the paraffin in xylene and rinsed off 

 the xylene with 95 % alcohol, as there directed, the slides may be set in 

 a tumbler or Stender dish containing safranin, for about 6 hours, or over 

 night, then quickly rinsed in 95 % alcohol, then placed in a tumbler of 

 xylene, thence mounted in balsam as directed below. Or the sections 

 may be double stained with cyanin and erythrosin, practically as directed 

 under that head ; leaving the slides over night in a tumbler of cyanin 

 solution, then rinsing in a tumbler of 95 % alcohol ; by means of a drop 

 tube covering the sections with clove oil saturated with erythrosin, while 

 holding the slide horizontal ; after a moment draining off the clove oil 

 and rinsing the slide in xylene, and then sealing the preparation in 

 balsam. 



But where the embryonic tissues of root and shoot tips, and develop- 

 ing pollen grains, ovules, etc., are to be studied with special reference to 

 the construction and behavior of the protoplasts, the most beautiful and 

 serviceable results in staining are achieved by the three-color method, 

 employing safranin, gentian violet, and orange G, made by Griibler and 



