GENERAL TECHNIQUES FOR CLASSES OF PLANTS 705 



Cotton blue (BaumwoUblau 4B) or anilin blue in laeto-phenol 

 are useful stains (see also § 1397). Maneval {Stain Tech., xi, 

 1936, p. 9) describes the use of several stains with Amann's laeto- 

 phenol or phenol glycerin. Fungi, alga% etc., are well stained in 

 laeto-phenol containing anilin blue, VV.S. (cotton blue) or acid 

 fuchsin, used singly or mixed. The addition of 20 to 25 per cent, 

 glacial acetic acid makes staining more rapid and less deep. 

 Delicate forms can be fixed and mounted in glycerin jelly, in 

 which a small quantity of stain {e.g. gentian violet or safranin) 

 has been dissolved. See also Davis, Phytopath., xii, 1922, p. 492 

 (staining germinating spores). 



For cytological details, staining in Heidenhain's hematoxylin 

 and counterstaining with Congo red or with light green, erythrosin 

 or orange G in clove oil has been most used. Newton's gentian 

 violet-iodine method would probably be advantageous with most 

 fungi. Gwynne-Vaughan and Barnes {The Fungi, 1927, p. 331) 

 also suggests Flemming's triple stain or gentian violet and orange 

 G alone ; they state that if the nuclei are reasonably large Breinl's 

 safranin-polychrome methylen blue-orange tannin combination 

 is by far the best. 



1396 bis. Staining Cell Constituents in Diseased Plant Tissues. 

 The greatest changes in affected cells of diseased tissues are likely 

 to occur in the vacuolar system. 



DuFRENOY {Stain Tech., iii, 1928, p. 57) therefore recommends 

 fixation with Meves or Regaud fluids where embryonic cells, 

 with dense cytoplasm, are to be studied cytologically in the 

 same section with vacuolated cells. It is best to stain with acid 

 fuchsin and destain with light green using Kull's method, pre- 

 ferably after Meves fixative. Post-staining with 0-5 per cent, 

 aqueous toluidine blue and destaining with 0-5 per cent, aurantia 

 in 70 per cent, alcohol give blue starch grains within red plastids. 

 See also Dufrenoy, Ann. Epiph., xiv, 1929, p. 227 ; Pelluet, 

 Ann. Bot., xlii, 1928, p. 637. 



1397. Differential Staining of Parasite and Host. This is often 

 diilicult. The usual histological combinations are often successful. 

 Gwynne-Vaughan and Barnes {The Fungi, 1927, p. 30) recom- 

 mend safranin and light green and also methylen blue and 

 erytlirosin. These combinations are especially successful with 

 hyphse in the xylem of the host. If the host is woody, a lignin 

 stain, preferably safranin or gentian violet, should be used, and 

 various contrasting stains tested until one is found that suits the 

 particular ease. The following special methods may be employed. 



Vaughan {Ann. Missouri Bot. Card., i, 1914, p. 241) uses the 

 stain mixture Pianese Illb, })repared from malachite green 

 0-5 grm., acid fuchsin 0-1 grm., martius yellow 0-01 grm., distilled 

 water 150 cc, 95 per cent, ethyl alcohol 50 c.c. Wash sections in 

 water or alcohol and stain them in the mixture for lifteen to 



VADE-MECUM. 23 



