202 BARKS. 



(99) Pomegranate Root Bark. 



The root bark of Punica Granatum, Linn. (N.O.Lythrarieee). 

 The bark exhibits the following structure : 



(1) Cork. The outer layers of this tissue are often much 

 flattened and in process of exfoliation ; the inner layers are 

 composed of flattened, tangentially elongated cells, the inner 

 tangential walls of which are thickened and pitted. In surface 

 view these cells appear polygonal, isodiametric, and pitted. 



(2) Cortex. The cells of the cortical parenchyma are 

 tangentially elongated, and contain a little chlorophyll, together 

 with starch grains, and occasional prismatic crystals of calcium 

 oxalate. Here and there, especially in old barks, large scleren- 

 chymatous cells are to be found ; they are usually isolated, 

 seldom in couples, very irregular in shape, and have very thick, 

 pitted walls. 



(3) Bast Ring. The bast ring is divided by one-celled 

 medullary rays into very distinct bast rays, which are 

 characterised by the great number of rosette crystals of calcium 

 oxalate contained in them. These crystals are contained in 

 the cells of the bast parenchyma, and, in transverse section are 

 arranged in parallel tangential lines, sometimes single, some- 

 times double, alternating with rows of similar cells containing 

 small starch grains. In longitudinal section the crystal cells 

 are seen to be in vertical rows. 



The root bark is distinguished from the stem bark more 

 particularly by its greater disposition to form an outer bark 

 by the production of secondary phellogens in the cortex. 

 The stem bark also bears lenticels ; these are filled with 

 layers of thick- walled cork cells, between which there are 

 numerous rounded cells with unequally thickened pitted walls 

 {Tschirch's choriphelloid cells). 



The diagnostic characters of powdered pomegranate root 

 bark are : 



(a) The large number and regular arrangement of the 

 rosettes of calcium oxalate. 



(6) The very large, thick-walled, pitted sclerenchymatous 

 cells.' 



(c) The inner layers of cork cells, thickened and pitted on 



one side. 



(d) The small isolated starch grains. 



