PEZIZIN PHLORIDZIN 355 



sections of plant tissues are treated for several hours with a mix- 

 ture of i part of hydrochloric acid and 4 parts of alcohol, the 

 calcium pectate becomes changed, so that pectic acid is liberated 

 and calcium chloride is formed. The pectic acid is insoluble 

 in water, but is soluble in a 10 per cent, solution of ammonia, 

 so that after rinsing the sections in water and treating with the 

 ammonia solution, the cells may be separated from each other 

 by a slight pressure on the coverglass. When the sections are 

 placed for a considerable time in cold alkaline solutions, a double 

 pectate is formed which swells in cold water and finally dis- 

 solves in it. After the calcium pectate of the middle lamella 

 has been removed, the pectose which permeates the cell-wall 

 still remains, but by treatment with cuprammonia it may be 

 removed from sections which have already been acted on by 

 dilute hydrochloric acid. The pectic substances may be stained 

 only in neutral or slightly acid solutions. For this reason it is 

 a good plan to place sections for a short time in a 3 per cent, 

 solution of acetic acid, and then to wash them in water before 

 transferring them to the staining solutions. Safranin, methyl- 

 ene-blue, bleu de nuit, and ruthenium-red are excellent stains 

 for pectic substances. Safranin stains the protoplasts and the 

 lignified, suberized, and cutinized cell-membranes a cherry-red, 

 while the pectic compounds are stained orange-yellow. Methyl- 

 ene-blue and bleu de nuit stain the protoplasts and the lignified 

 membranes blue, and the pectic substances a violet color. See 

 also in the last chapter under Ruthenium-red. 



Pezizin. Pezizin is an orange-red coloring matter which 

 occurs in solution within the paraphyses of Peziza aurania and 

 P. convexula. It is soluble in alcohol and ether, and is not 

 altered by alkaljes and organic acids. It dissolves without color 

 in hydrochloric acid and is colored bright green by nitric acid. 



Phloridzin, C 21 H 24 O 10 . A glucoside occurring in the leaves 

 and in the cortex of the roots and stems of the Pomacea?. When 

 tissues of Pirus malus containing phloridzin are treated with 

 ferric chloride, a dark brown solution is formed, while treatment 

 with ferrous sulphate causes a yellowish-brown precipitate. 



