680 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



[Vol. 2 



off, the sections must not be allowed to become dry or an 

 orange precipitate is obtained that necessitates the addition 

 of alcohol to dissolve it. This also dissolves the stain from 

 the tissues and the sections must be restained. This pre- 

 cipitate is not formed if a little water is added to the stain 

 after it is made up. This stain imparts a uniform dull red 

 color to the tissue but the color brightens when glycerin is 

 drawn under the cover glass. Since it is not a differential 

 stain its use is not advised where only temporary mounts are 

 desired. It gives best results with very thin sections or with 

 sections in which the hyphae are loosely arranged. 



After the cover glass is applied the sections are ready to 

 be examined under the microscope, but if the saffranin T 

 stain is used, it is better to place a drop of glycerin at one 

 side of the cover glass, at the same time drawing off some of 

 the surplus water from the opposite side by means of filter 

 paper. Several slides of each species are retained and 

 mounted in 66 per cent glycerin. After a week or more all 

 traces of the glycerin are removed from near the outer edge 

 of the cover glass by means of a soft cloth dipped in 95 per 

 cent alcohol. The slides are then ringed with some suitable 

 cement — gold-size being most often used — labeled, and filed 

 away in order. It will usually facilitate subsequent examina- 

 tion of the slides if the spore characters for each species are 

 written on a slip of gummed paper and glued to one end of 

 the slide. 



It is sometimes quite impossible to find spores in the sec- 

 tions treated in the manner outlined above, since they are 

 often easily removed from the sterigmata and washed away 



cover glass is applied. To overcome this difficulty 

 sometimes finds it advisable to distribute between 



before the 



two slides the sections obtained, one slide to be treated as 

 outlined above, the other to be mounted for temporary ob- 

 servation only. This last one should be stained with a water 

 solution of 1 per cent eosin, a drop of the solution being added 

 to the drop of KOH containing the sections. Sometimes the 

 staining is unnecessary, especially if one is dealing with 

 species which have colored hyphae and colored spores. A 



