I30 



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It is interesting to note that many cells in the thick cork layer of the bark 

 contain some mucilage and crystals and they are alread\' differentiated when found 

 in the layer next to the cork-cambium. By the reaction with phloroglucin and 

 hj'drochloric acid, it can be proved that their cell-walls show the ligniRcation, 

 in contrast to the fact that the cell-walls adjacent to those mentioned react as the 

 suberized membrane. Sudan III as well as several reagents for cellulose can not 

 stain the cell-wall of the rapJiides-containing cell. When it is placed between 

 crossed nicols, and the gypsum plate is inserted, the interference colour shown by 

 the cell-walls becomes higher, in the .same direction with the greatest elasticity 

 axis of gypsum ; while other cells in the layer show the lower interference colour 

 and can be stained with sudan III. 



From the foregoing statement, I can conclude that it is impossible to obtain 

 mucilage from the stem merely by injuring the bark like the method usually adopt- 

 ed in the collection of gum arabic and its allies. As the bast of the stem contains 

 mucilage most abundantly, it is advisable to utilize this layer cliiefly ; next to this, 

 the bark can not be neglected if it is freed from dirty admixtures. In comparing 

 the numbers of the crystal-containing cells with one another, older stems are 

 preferable. 



