﻿1903] RAVENELIAS OF THE UNITED STATES 113 





found necessary, prepared as follows: A mixture of equal parts 

 of 100 per cent, glycerin and 80 per cent, alcohol was made, 

 and a glass slide was used on which a cell of white zinc had been 

 made. It was found necessary to make the cells two layers thick 

 in order to get the proper depth, putting on as much zinc each 

 time as would stay without spreading too much; an interval of 

 one to two hours between the putting on of the two layers is 



, required. The slide was laid aside until the cell became dr^-and 



hard. In the center of this cell a scant drop of the glycerin 



i and alcohol mixture was put; into this the spores, etc., were 



put; then a drop of 50 per cent. lactic acid was added and 

 the slide heated over an alcohol lamp until the liquid came to a 

 boiU In some cases it is necessary to boil it for a short time to 

 make the germ pores show plainly. Care had to be taken not 

 to boil so long as to burst the cysts, and yet to boil until the 

 germ pores were visible; usually bringing the mixture to a boil 

 accomplished the desired result. The mixture of alcohol and 

 glycerin as given above prevents the bursting of the cysts, which 

 usually happens in a water mount, while the acid makes the 

 germ pores visible. After the preparation had cooled a cover 

 glass was put on and sealed with white zinc. This makes a neat 

 permanent mount, ready for instant use at any time, and shows 

 practically all the desired details. 



To ascertain whether the sori are subepidermal or subcutic- 

 ular, microtome sections should be made. Most of the speci- 

 mens will be dry and must be softened before they can be 

 imbedded. A good method for softening the tissues is to place 

 them in a mixture of equal parts of 65 per cent, alcohol and 100 

 per cent, glycerin ; then heat this in the paraffin oven for 

 twenty-four to forty-eight hours, at the end of which time the 

 tissues will usually be soft and pliable; then wash in 65 per cent, 

 alcohol for six hours ; then run up and into paraffin in the usual 

 manner. Bismarck brown or methyl blue makes a good stain for 

 such preparations where the main object is to see the position of 

 the sori. The cysts would often come through the entire pro- 

 cess and show up beautifully in the Canada balsam mount. 



The boilincr in lactic acid is desirable for several reasons; 



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