PYRENOIDS RESERVE CELLULOSE 359 



as already suggested. Sulphuric acid may be used instead of 

 the chloroiodide of zinc as the swelling agent. For demon- 

 stration purposes sections through the endosperm of the Gram- 

 ineae, or tangential sections through the green bark of Rhamnus 

 frangula, may be used. Sections are placed on a coverglass in 

 a drop of sulphuric acid. After a few seconds the acid is washed 

 away by immersing the coverglass and moving the -sections 

 about in a dish filled with water. The sections remain in the 

 water for only a short time, and are then to be stained in an 

 aqueous solution of aniline blue, washed in water, and mounted 

 for examination in dilute glycerine. Or the sections may be 

 stained in a saturated solution of picric acid in 50 per cent, 

 alcohol, to which aniline blue is added until the solution has a 

 blue-green color. 



Pyrenoids. The pyrenoids may be simultaneously fixed 

 and stained by placing the material in a concentrated solution 

 of picric acid in 55 per cent, alcohol, to a watch-glass of which 

 is added about 5 drops of the acid fuchsin and aniline water 

 solution described on page 302. The material should remain 

 for about 2 hours in a watch-glass of this solution. It should 

 then be washed for a quarter of an hour in alcohol and mounted 

 for examination in dilute glycerine. If permanent mounts 

 are desired, the material should be placed in a watch-glass 

 of dilute glycerine, which should then be allowed to concen- 

 trate in a place free from dust. The material should finally 

 be mounted in glycerine-jelly. The material may be mounted 

 in Canada balsam by transferring it from the alcohol in which 

 it was washed to successively stronger solutions of balsam in 

 xylol until the ordinary solution used for mounting is reached. 



See under Dahlia in the previous chapter for other methods 

 of treating pyrenoids. 



Reserve Cellulose. Those hemicellulose thickenings of 

 cell-walls in seeds, etc., which are essentially reserve food mate- 

 rials, and are made soluble by diastatic ferments, and employed 

 as food material in the germination of seed, are known as reserve 

 cellulose. Sections taken from a sprouted date seed and treated 



