158 



PLANT ORGANS OR PARTS OF PLANTS. 



The cork cells are in abundance and are of interest; 

 they vary in size from about 1 5 to 2 5 microns and often are 

 found isolated. 



Bast fibres are found, in fragments, depending upon 

 the fineness of the powder ; they are usually colored some 

 shade of yellow or brown, are about 5 to 15 microns in the 



0O.»", 



) i>ep°» 



Fig. 39. — Powdered Cascara. 

 C, Crystals, two kinds; B, bast fibre with crystal sac; Cr., Cor, 

 cork; P, PAR, parenchyma with starch; ST, stone cells; M, medullary 

 rays; S, starch; O, tissues of phloem. 



short diameter and contain clustered cubical crystals in 

 small crystal sacs, one crystal to a sac, along their long 

 diameter. 



The parenchyma tic tissues vary widely. Those of the 

 middle bark are usually wider lumened and average about 

 20 microns in diameter and about 40 microns in length. 

 The cell walls are delicate, those nearer the outer bark 



