METHYLENE-BLUE 313 



under a coverglass. Bast and wood fibers and stone cells can 

 be isolated by this process, but thereafter they give the reaction 

 for cellulose instead of for lignin. 



Another process, known as the Mangin process, gives good 

 results with sections. Place the sections for forty-eight hours 

 in a mixture of four Nolumes of alcohol and one volume of 

 hydrochloric acid. Wash the sections in water and put them 

 into 10 per cent, ammonia for fifteen minutes, then mount a 

 section in a drop of water under a coverglass and press upon 

 the coverglass until the cells are forced apart. 



Chromic acid also is used for maceration. Place sections 

 in a concentrated solution for a minute or so, then rinse them 

 in water, mount them in a drop of water under a coverglass 

 and press upon the coverglass. If the cells do not then come 

 apart they should be put for a longer time in the acid. 



Methyl-blue. — An aqueous solution is an excellent stain 

 for cellulose membranes. It may be used as a double stain 

 with safranin as follows: Stain in safranin over night (see under 

 Safranin) and then rinse in water and acidulated alcohol; place 

 in a concentrated aqueous solution of methyl-blue for fifteen 

 minutes, rinse in strong alcohol and xylene and mount in balsam. 

 See also under Fuchsin. 



Methylene-blue. — A good nuclear stain. For cells filled 

 with protein granules it is particularly good in dilTerentiating 

 the nucleus. Methylene-blue is useful in differentiating pectin 

 compounds. The protoplast and lignified walls are stained a 

 bright blue, while pectin compounds are stained a violet blue. 

 Cells containing tannin will accumulate methylene-blue from 

 very dilute solutions. The sections of living tissues are placed 

 in a solution of i part of the stain in 500,000 parts of filtered 

 rain-water. The cells containing tannin soon take on a distinct 

 blue color, and, later, a deep blue precipitate is formed in them. 

 The gelatinous sheaths of live conjugatae may be stained by 

 dilute aqueous solutions of methylene-blue without injury 

 to the living organism. A o.ooi per cent, solution of methylene- 

 blue in water will stain the living nuclei of diatoms and other 



