ro u 5 0*1© !Ä;ß r- a 



It is interesting to note that many cells in the thick cork Ia\'er of the bark 

 contain some mucilage and crj'stals and the_\' are ahead)- differentiated when found 

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

 hydrochloric acid, it can be proved that their cell-walls show the lignification, 

 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 raphides-containing cell. When it is placed between 

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

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

 axis of gypsum ; while other cells in tlie la\"er 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 arable and its allies. As the bast of the stem contains 

 mucilage most abundantly, it is advisable to utilize this layer chiefly ; 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. 



