GENERAL TECHNIQUES FOR CLASSES OF PLANTS 701 



3. Direct manipulation of the cell by (a) removing it on an 

 agar surface to some other part of the surface ; 



Dickinson, Ann. Bot., xl, 1926, p. 273 (micro-isolator). 



(b) lifting it bodily from a strewn preparation on a slide. 



Hanna, Ann. Bot., xxxviii, 1924, p. 701, and Newton, Arm. Bot., xl, 

 1926, p. 109 (dry needle method) ; Dunn, Phytopath, xiv, 1924, p. 338 

 (micro-loop) ; Edgerton, Phytopath, iv, 1914, p. 115. 



4. Sterilisation of all cells except the selected one The 

 selected cell is covered with a mercury droplet and the rest 

 killed by ultra-violet light. 



TopLEY, Barnard and Wilson, J. Hyg., Camb., xx, 1921, p. 22; 

 Barnard, Brit. J. Exp. Path., vi, 1925, p. 39. 



5. Preparation of a dilute suspension in a capillary tube. 

 Hansen {Science, Ixiv, 1926, p. 384) breaks the tube into short 



lengths, selects those containing a single cell, sterilises them 

 with alcohol and drops them into culture medium. Gupta 

 (Brit. Myc. Soc. Trans., xix, 1935, p. 154) makes tiny droplets on 

 a suitable surface by quick light touches and selects those con- 

 taining a single cell only. 



6. Single strains of fungi may be isolated by cutting out a 

 hyphal tip and transplanting it to a suitable medium. Any 

 suitable mechanical device can be used. See Brown (Ann. 

 Bot., xxxviii, 1924, p. 401) who also describes a method for freeing 

 fungal cultures from bacterial contamination ; and Machacek 

 {PhytojMth., xxiv, 1934, p. 301). 



1393. For general fixation use absolute alcohol, saturated 

 corrosive sublimate with 1 per cent, acetic in 95 per cent, alcohol, 

 or Gilson's fluid, which is particularly good for fleshy forms. 



Oltmann (Stoin. Tech., x, 1935, p. 198) recommends a dilute 

 (2 to 3 per cent.) solution of secondary butyl alcohol. 



DuGGAR (Fungous Diseases of Plants, 1909) recommends a modified 

 Gilson : 95 per cent, alcohol, 30 c.c. ; glacial acetic acid, 2 c.c. ; nitric 

 acid, 5 c.c. ; mercuric chloride, 10 grm. ; distilled water, 270 c.c. 



Follow the usual procedure after a mercuric fixative. Chamberlain 

 (1932, p. 261) recommends hot (85° C.) corrosive sublimate-acetic acid 

 (corrosive sublimate, 2 grm. ; glacial acetic acid, 2 c.c. ; and water, 

 100 c.c). Fix for one minute. AVash in water and add iodine solution 

 a few drops at a time, until it is no longer decolourised. Then stain. 



See also : Gilbert, Bull. Soc. Mycol. France, xlv, 1929, p. 141 

 (iodine vapour). 



Ewart's Method for the Preservation of Fleshy Fungi {Ann. 

 Bot., xlvii, 1933, p. 579). Soak material in a mixture of 2 parts 

 of formaldehyde to 1 of liquid carbolic acid and after superficial 

 drying suspend the specimen over strong ammonia until it sets 

 solid without drying. The appearance is somewhat like that of 



