GENERAL TECHNIQUES FOR CLASSES OF PLANTS 695 



serves and mounts in a 2 per cent, solution of potassium acetate, 

 just made blue with a small amount of copper acetate ; for 

 mounting, Nicuwiand adds an equal volume of 10 per cent, 

 jjlvcerin and allows it to concentrate. 



Flemming type fluids are best for details ; use the weaker 

 formuke, especially on filamentous forms. 



Sublimate fixatives give good results with alga?, and are fre- 

 quently best used hot. Try a saturated solution of corrosive 

 sublimate in 70 per cent, alcohol (Fergusson, Ann. Bot., xlvi, 

 1932, p. 703). Carter {Ann. Bot., xxxiii, 1919, p. 213) fixes 

 desmids in a mixture of 3 grm. corrosive sublimate, 3 c.c. glacial 

 acetic acid and 100 c.c. 50 per cent, alcohol ; use hot and replace 

 at once with several changes of 50 per cent, alcohol. For Clado- 

 phoraccfe, reduce the acetic acid to 1 c.c. (Carter, Ann. Bot., 

 xxxiii, 1919, p. 467). 



Many Myxophyceae do not fix well. Oscillatoria and hormo- 

 gonia of other genera can be induced to creep on to a slide ; then 

 fix in situ. Large fleshy Pha;ophycese and Rhodophyceae should 

 be cut into small pieces for accurate fixation. 



Fix marine forms in solutions made up in sea-water. P^or 

 general preservation use 4 c.c. formalin (40 per cent, formaldehyde) 

 in 96 c.c. sea-water, or for more critical work 25 c.c. 1 per cent, 

 chromic acid in sea-water, 100 c.c. 1 per cent, glacial acetic acid in 

 sea-water, 65 c.c. sea-water. Higgins {Ann. Bot., xlv, 1931, 

 p. 345) doubles the volume of acetic acid used in the case of some 

 forms {e.g., Stypocaulon) and reduces the sea-water by 10 c.c. 

 Wash in sea-water and transfer to fresh water (see dehydration). 



Preserve in 50 c.c. alcohol, 4 per cent, formalin, Keefe, or gly- 

 cerin. 



Alsterberg {Bot. Notiser, 1927, p. 71) finds bromocyanin an 



excellent preservative of filamentous algae. 



Diatoms encrusting material can be removed with hydrofluoric 



acid. 



See also von Wellheim, Jahrb. Wiss. Bot., xxvi, 1894, p. 674 . 



Lemmermannt, Kryptogamenflora Mark Brand, iii, 1910, p. 12 ; 



Smith, Plant World, xvi, 1913, p. 219 ; Tiffany, Trans. Amer. 



Micr. Soc, xlv, 1926, p. 69 ; Lucas, Science, Ixx, 1929, p. 482 ; 



Lerour, " The Dinoflagellates of Northern Seas," Marine Biol. 



Assoc. U.K., Plymouth, 1925, 250 pp. ; Chamberlain, Publ. 



Puget Sound Biol. Stat., V, 1928, p. 319 (microtechnique for 



marine algre). 



1379. For preserving Myxophyceae and Rhodophycea? in their 

 natural colours, Kirchner {Die mikr. Pflanzenwelt des SiXsswassers. 

 Braunschiteig, 1885) mounts in dilute glycerin, to which sufficient 

 chrome alum (chromium-jjotassium sulphate) is added to give the 

 fluid a clear bluish colour. 



1380. Staining, Most useful are Heidenhain's ha^matoxylin, 



