GENERAL TECHNIQUES FOR CLASSES OF PLANTS 703 



Green {Atm. Bot., xli, 1927, p. 421) transfers Zygorhynchus, 

 after fixing and washing, to 10 per cent, aqueous glycerin to 

 which a drop of dilute acetic acid and 2 to 3 drops of saturated 

 aqueous erythrosin have been added. Allow to concentrate in 

 watch-glass and then mount in glycerin jelly. 



Chamberlain (Methods, 1932, p. 261) gives a rapid glycerin 

 mounting method for use with small forms. Fix two minutes 

 in absolute alcohol. Stain two minutes in aqueous eosin solution 

 and treat two to ten seconds in 1 per cent, acetic acid. Mount 

 directly in 5 per cent, glycerin and seal. If the material collapses 

 in the glycerin, put into 10 per cent, glycerin and allow to 

 concentrate. 



In the preparation of minute objects for sectioning, the use of 

 a centrifuge is advantageous. Colley {J. Agric. Res., xv, 1918, 

 p. 619) describes a method for imbedding such material in paraffin 

 while in the centrifuge. 



Harper's method for handling such small structures is useful 

 for many purposes, including the study of germinating spores 

 and conidia. Make cultures in beerwort or other liquid medium 

 on slides or in watch-glasses. Take up a drop of the suspension 

 with a capillary tube and gently blow it out into a drop of weak 

 Flemming fixative. Fix fifteen minutes to one hour or more. 

 Smear a clean slide with Mayer's albumen. Draw up a drop of 

 the material, without previous washing, into the capillary tube. 

 Touch the tube quickly and lightly on the surface of the albumen, 

 to leave minute dots of liquid containing material attached to 

 the slide. Allow the fixative to evaporate somewhat, but do not 

 let the preparation dry. Pass the slide rapidly through the 

 alcohols to coagulate the albumen. Treat the slide now as though 

 it carried sections. 



Cultures of small forms (including bacteria) and germinating 

 spores may also be treated as follows : (1) Spread a film on a slide, 

 dry and fix by passing the slide a few times quickly through a 

 flame, then stain ; or (2) spread a film on a slide previously 

 smeared with albumen and allowed nearly to dry ; immediately 

 invert flatly on fixing fluid in a fixing dish. Afterwards, wash and 

 treat as a smear. 



Bachmann's Method {Amer. J. Bot., v, 1918, p. 32). Prepare 

 clean sterile slides. Pour on to one slide a little of a culture 

 medium (having an agar or gelatin base), inoculated with a 

 suspension of the organisms to be examined. Place another slide 

 on the first and draw them apart, leaving quite a thin film. 

 Incubate the slides under sterile conditions in a damp chamber, 

 e.g. in a Petri dish lined top and bottom with wet filter-paper. 

 When the colonies are ready, fix and stain as for a smear. All 

 media must be cleared for this method. She recommends potato 

 broth agar for yeast. 



