48 CULTURE METHODS AND TECHNIQUE 



is a tendency to make the sections too thin when this method is 

 employed. Some thin sections will usually be required, but for such 

 studies as the distribution of the fungus in the host, and the forms 

 and relations of fruiting organs, thicker sections are preferable. 



Attaching sections. Since the paraffin method is here presented 

 in some detail, a few indications with reference to fixing sections to 

 the slide and the further manipulation of the material will be 

 requisite. A minute drop of egg albumen preparation 1 is first 

 rubbed over that portion of the slide to which the sections are to 

 be affixed. Add a few drops of water from a pipette, arrange the 

 sections or ribbon exactly as may be desired on the slide, allowing 

 for expansion to their normal size, and place the slide immediately 

 in the paraffin oven, that is, at a temperature which will just melt 

 the paraffin (Strasburger's method). In two hours the slides will 

 be ready for removal and for the subsequent processes. The method 

 mentioned is simpler and better than the one in which more 

 water is added when the sections are laid on the slide, the slide 

 warmed over a flame until the sections spread out, the water drained 

 off, and finally the slides set aside from four to twenty-four hours 

 to dry in a warm place. In either case, when the slides are 

 thoroughly free of moisture, they are passed into the xylol for a 

 few minutes, then into absolute alcohol, and to such other grades 

 as are necessary prior to staining. In all of these processes Cop- 

 lin's staining jars or other similar vessels are desirable. Care 

 should always be taken to remove every trace of paraffin before 

 proceeding further. 



III. STAINING 



Filamentous fungi. It is often necessary to employ staining 

 methods in an examination of hyaline filamentous fungi, even if 

 the observation is merely for the provisional determination of the 

 fungus at hand. This is particularly true in an examination of 

 certain mold or hyphomycetous fungi. Such fungi, and particu- 

 larly the aerial parts of such fungi, should be well teased out in a 

 drop of weak acetic acid, or sodium hydrate in 10 to 20 per cent 

 alcohol, on the slide. This killing agent is drained off by means 

 of filter paper, the preparation washed, and then it may be stained 



1 Egg albumen, 50 cc. ; glycerin, 5 cc. ; and salicylate of soda, \ gram. 



