640 SOME SPECIAL METHODS 



chlorine in 50 per cent, alcohol ; eau de Javelle ; saturated solu- 

 tion of sulphurous acid in alcohol ; dilute potassium perman- 

 ganate followed by oxalic acid and exposure to light. 



1267. Chemical clearing methods are used whenever the presence 

 of the cell contents is unnecessary, in order to make the tissue 

 masses as transparent as possible. Chiefly used are KOH, phenol, 

 chloral hydrate (CCl3.CH(0H)y) and eau de Javelle (potassivmi 

 hypochlorite). Prepare eau de Javelle by adding a solution of 

 potassium oxalate to a concentrated aqueous solution of chloride of 

 lime for as long as a precipitate is formed ; filter and dilute for use. 



Clearing Whole Organs or Thick Sections. Simpson {Stain 

 Tech., iv, 1929, p. 131) uses lactic acid, in a concentration of 

 about 75 per cent. Immerse whole flowers or large parts, such as 

 pistils, in open watch-glasses. Mount fairly thick hand-sections 

 of fresh material in acid on a slide. Then place the specimen in 

 a constant temperature oven at about 54° C. until clear. The time 

 required varies ; sections of floral parts, young fruits and succu- 

 lent stems require two to three hours ; whole parts or thick wedges 

 of such material take about twelve hours. If permanent slides 

 are desired, allow the lactic acid to thicken slowly in the oven 

 until it is almost hard. Then seal the edges of the preparation 

 with a mixture of gum mastic and paraffin. Clean up slides with 

 the aid of alcohol. See also Seshadi and Aiyakgar {Indian J. 

 Agric. Sci., ii, 1932, p. 51). 



Bates {Amer. Nat., Ixv, 1931, p. 288) clears leaves by 

 treating them with a saturated solution of chloral hydrate for 

 forty-eight hours, then with potassium chlorate and nitric acid for 

 ten to thirty minutes and finally with potassiuin chlorate and 

 chloral hydrate for a week. Quick and Patty {Phytopath. xxii, 

 1932, p. 925) bleach and clear leaves by processing them, in an 

 airtight container, in an aqueous solution of commercial sodium 

 hypochlorite and lye. McVeigh {Stain. Tech., x, 1935, p. 33) uses 

 5 per cent, sodium hypochlorite solution for clearing leaves. See 

 also : Peace, Plant World, xiii, 1910, p. 93. 



Strain {Phytopath., xxiv, 1934, p. 82) bleaches leaves and petals 

 quickly by means of alcohol containing nascent chlorine. The 

 material is afterwards cleared, e.g. in Ainann's medium. 



1268. Staining the Vascular Bundles in Whole Organs. Barratt 

 {Ann. Bot., xxxiv, 1920, p. 201) treats Eqnisetiun seedlings with 

 eau de Javelle for twenty-four hours in the cold. Wash in water 

 and stain in ammoniacal fuchsin by Zimmermann's method. 

 Dehydrate, clear with clove oil and mount in balsam. Mounting 

 in glycerin jelly or euparal renders the walls of the parenchyma 

 more visible. Apices and mature shoots may also be successfully 

 treated, but slit these longitudinally into two halves before 

 clearing and mount in a cell with the interior of the stem upper- 

 most. 



