FUNGI 271 



eery may be preserved in formalin alcohol (6 c.c. of formalin to 100 

 c.c. of 50 per cent alcohol.) When formalin is used in water, the fungi 

 become too soft. Larger forms of the mushroom, puffball, and bracket 

 types may be dried in an oven. The circulation of air should be good, 

 and the temperature should be kept at about 50° C. After drying, the 

 fungi should be poisoned. 



For sections, Gilson's fluid deserves more recognition than it has 

 received. It is particularly good for soft forms, like Treniella. 



Gilson's fluid. — 



Ninety-five per cent alcohol 42 c.c. 



Water 60 c.c. 



Glacial acetic acid 18 c.c. 



Concentrated nitric acid 2 c.c. 



Corrosive sublimate (saturated solution in water) . . 11 c.c. 



Fix about 48 hours and wash in 60 or 70 per cent alcohol. 



Coprinus niicaceus is particularly good for a study of gills, basidia, 

 and the formation of basidiospores, because it is so small that a single 

 section may show a fine series of stages. Gills which are becoming 

 brownish at the tip, but which are still white toward the top of the 

 cap, will show a splendid series of stages, as will also pieces cut from 

 gills which are brownish at the edge, but white farther back. For fix- 

 ing, cut out pieces 1 cm. long and 3 mm. thick. If pieces are taken into 

 the mouth and wet with saliva for 30 seconds, the fixing agent pene- 

 trates better and there is scarcely any danger that air may be caught 

 between the gills. The Chicago chromo-acetic-osmic formula is good 

 for fixing any of the fleshy fungi. 



To show the four basidiospores attached to the basidium, sections 

 should be 10-15 n thick; but to show nuclear detail, 2 or 3 ;u is thick 

 enough (Fig. 75). 



In Hydnum and Polyporus, cut out pieces about 3 or 4 spines or 3 

 or 4 pores in width and about 1 cm. long. A rectangular piece which 

 will allow the transverse sections of the spines or pores to be about 4 

 mm. wide and 1 cm. long cuts better than a piece which will give 

 square sections. 



In Boletus, simply strip off the hymenium and cut into pieces which 

 will give transverse sections of the tubes. 



In Lycoperdon, Bovista, Geaster, and Scleroderma, longitudinal sec- 

 tions of the entire fructification can be cut in paraffin as long as the 

 fresh material is easily sliced with a safety razor blade. 



