SOME SPECIAL METHODS 647 



staining or the staining of other tissues wash in alcohol, used pure 

 or slightly acidulated with HCl. See Kisser, Zeit. wiss. Mik., 

 xlv, 1928, p. 103 ; Tisox, C.R. Assoc. Franc. Av. Sci., xxviii, 

 Pt. 2, 1895), p. 454 ; Priestley, Xeic Phijt., xx, 1921, p. 17. 



Cutin is very resistant to acid hydrolysing agents, but is readily 

 oxidised by either acid or alkaline oxydising agents. The best 

 stain for it is 1 per cent, alcoholic Sudan III. ; heat sections on 

 the slide until the alcohol boils. For delicate cuticles use Nile 

 blue sulphate or dimethylaminoazobenzene. See Lee and 

 Priestley, Ann. Bof. xxxviii, 1924, p. 525. 



1282. Callose (see Mangin, Compt. rend., ex, 1890, p. 644) occurs 

 principally in sieve plates of the phloem, in pollen grains and 

 tubes and in fungal hyphge. It is insoluble in water, alcohol, 

 cold alkali carbonates, ammonia and Schweizer's reagent, but very 

 soluble in 1 per cent. NaOH or KOH, concentrated H2SO4 and 

 concentrated calcium chloride and tin chloride solutions. Iodine 

 colours it yellow, chlor-zinc-iodide brick red or red brown. It is 

 strongly stained by a dilute solution of corallin in 4 per cent, 

 aqueous sodium carbonate, by dilute aqueous anilin blue 

 followed by dilute HCl, and by a number of other anilin dyes, 

 especially after alkali treatment or oxidation. 



1283. Chitin is a constituent of fungal cell-walls. Use Van 

 Wisselingh's [Jahrh. Wiss. Bot., xxxi, 1898, p. 657) chitosan 

 reaction. Seal material in glass tubes with glycerin and heat to 300° C. 

 in an oil bath. Then treat in concentrated or 50 per cent. KOH 

 at 160° to 180° C. for twenty minutes and wash on slide with 95 per 

 cent, or absolute alcohol. Bring to distilled water, treat with 

 aqueous iodine solution and then with 1 per cent. HgSO^. Chiti- 

 nous walls then stain violet red, the colour disappearing in 70 

 per cent. acid. If cellulose is present a blue colour then develops. 



A less intense blue-violet colour is obtained with iodine- 

 potassium iodide solution and zinc chloride or chlor-zinc iodide. 

 See § 1183; see also Hopkins, Trans. Wis. Acad. Sci., xxiv, 1929, 

 p. 187. 



1284. Chloramine Test for Nitrogen in Cell-wall (Wood, Ann. 

 Bot., xl, 1926, p. 1 ; xli, 1927, p. 281). Submit sections to chlorine 

 gas for a prolonged period and treat with sodium phosphate and 

 potassium iodide solutions. The presence of protein is indicated 

 by the liberation of iodine. In lignified tissues the colour passes 

 from yellow to brown and finally to pink. 



1285. Latex and Latex Vessels. Material containing latex must 

 be collected in a manner to minimise loss of the latex before 

 fixation is effected. Where there are long latex tubes, ligature the 

 stem near the places where it is to be cut and preserve in 50 per 

 cent, alcohol without removal of the ligature until hardening is 

 complete. Longitudinal sections are usually best. Stain in a 

 dilute aqueous iodine solution, followed by aqueous cosin or 



