196 BARKS. 



(96) Condurango Bark. 



The bark of Gonolobus Condurango, Triana (N.O. Asclepiadeee). 

 The bark presents the following structure : 



(1) Cork, of moderate thickness, composed of flattened, brown, 

 tabular cells, which in tangential section are polygonal in 

 outline. 



(2) Phelloderm, also of moderate thickness, characterised by 

 the presence of an abundance of prismatic or octohedral 

 crystals of calcium oxalate. 



(3) Cortex, the outer layers of which, abutting on the phello- 

 derm, are collenchymatous. The cells of the cortical 

 parenchyma are irregularly polygonal and contain small starch 

 grains and rosettes of calcium oxalate measuring mostly from 

 8 to 20/i in diameter. The cortex also contains numerous 

 laticiferous cells filled with a brown latex. 



(4) Bast Ring, which, especially in young barks, is separated 

 from the cortex by a ring of rounded bundles of thick-walled 

 pericyclic fibres (primary bast fibres). The bast ring is traversed 

 by narrow medullary rays, some of which are abruptly 

 enlarged towards the cortex. The bast rays contain numerous 

 laticiferous cells and sieve tubes, as well as large, irregular 

 groups of sclerenchyrnatous cells, the walls of which are very 

 thick, and have branching pits ; these groups are bordered by 

 cells with moderately thick pitted walls. The sieve tubes are 

 rather large and have oblique sieve plates. The bast parenchyma 

 is rich in starch grains and rosette crystals of calcium oxalate. 



The diagnostic characters of condurango bark are : 



(a) The laticiferous cells with brown latex. 



(b) The sclerenchyrnatous cells. 



(c) The pericyclic fibres . 



(d) The abundant, calcium oxalate in single crystals or 



rosettes. 



(e) The large sieve tubes with oblique plates. 

 (/) TJie starch grains. 



