702 GENERAL TECHNIQUES FOR CLASSES OF PLANTS 



a candied fruit. The shape and structure are fully preserved, 

 and by soaking in alcohol or water the whole of the impregnating 

 material can be dissolved away. Impregnated specimens heated 

 to over 100° C. are bakelised and become unaffected by water. 



See also Ulbrich, Zeits. Pilzkunde, v, 1926, pp. 105 and 143, 

 who gives details of the value of different antiseptics and of 

 colour preservatives for particular kinds of fungi ; and Stover, 

 Trans. III. Acad. Sci., xxi, 1929, p. 187. 



1394. Methods of Preparation. Many fungi, especially from 

 cultures on solid media, are in the form of a loose mass of hyphie. 

 Removal of air is accomplished by flooding material on a slide 

 with liquids of low surface tension, e.g. 0-5 per cent, gelatin or 

 soap solutions or 70 per cent, alcohol. Mount for morphological 

 examination in water, 3 per cent, acetic acid, 3 per cent, caustic 

 potash or dilute chloral hydrate. Aqueous media of low refractive 

 index are best. Use lactophenol (see also Linder, Science, Ixx, 

 1929, p. 430) or glycerin for stained material, or treat by the 

 Venetian Turpentine or Balsam Infiltration Methods. Cyto- 

 logical details are best studied in material fixed with a Flemming 

 fluid. Webb {Ann. Bot, xlix, 1935, p. 41) finds La Cour's 2B 

 best for Sorosphcera (Plasmodiophorales). Jones {Ann. Bot., xl, 

 1926, p. 607) and others use strong Flemming diluted with an 

 equal volume of water. Duggar {Fungous Diseases of Plants, 

 1909) gives a special Flemming formula : 10 per cent, chromic 

 acid 1-5 c.c. ; 10 per cent, acetic acid 1 c.c. ; 2 per cent, osmic 

 acid in 2 per cent, chromic acid 5 c.c. ; distilled water, 37-5 c.c. 

 He prefers to bleach in bulk in 3 parts of 95 per cent, alcohol 

 plus 1 part of hydrogen peroxide before imbedding. Filamentous 

 types are extremely delicate, and must be handled very carefully 

 through the alcohol grades and in imbedding. Duggar recom- 

 mends the use of small dipper-shaped wire gauze ladles, the 

 material being transferred undisturbed in the dipper. 



Minute forms, such as yeasts and germinating spores may be 

 handled in bulk. The material must be cultured in fluid media 

 and killed in bulk, with a suitable fixative, depending upon the 

 nature of the work intended. Wash in water or alcohol (depend- 

 ing upon the fixative employed) and grade into absolute alcohol. 

 Place a drop of suspension on a coverslip and allow nearly to 

 dry. Then flood the coverslip with water and allow the organisms 

 to settle. Drain away the water and allow the cover to dry. 

 Thorough drying should cause yeasts and other small structures 

 to adhere. Then wet cover, stain and mount. Alternatively fix 

 and then stain in Heidenhain's ha?matoxylin, dehydrate in gly- 

 cerin by concentration and infiltrate with balsam. 



Hook and Briggs {Science, Ixxx, 1934, p. 142) fix and stain 

 germinating conidia of Peronosporales in iodine-potassium iodide 

 solution (1 grm. iodine, 2 grm. KI and 300 c.c. water). 



