242 RHIZOMES AND BOOT 



(116) Jalap Root. 



The root of Ipomaa Purga, Hayne (N.O. Convolvulaceae). 

 The root presents the following structure : 



(1) Cork, composed of a rather thick layer of flattened, brown, 

 tabular cells which, in surface view, are polygonal and isodia- 

 metric. 



(2) Cortex, of moderate extent, the cells of which are polygonal 

 and contain starch and calcium oxalate. The starch occurs in 

 both simple and compound grains ; the former are rounded and 

 have a stellate hilum, the latter vary very much in size and 

 shape, according to the number of the component grains. This 

 tissue also contains numerous resin cells. These appear 

 rounded or oval in transverse section ; in longitudinal section 

 they are seen to be axially elongated and superposed in vertical 

 rows ; they contain a brownish resin. The cortex also contains 

 sclerenchymatous cells with thick, pitted walls. 



(3) Bast Ring, narrow and rich in resin cells and stellate 

 crystals. 



(4) Wood, which is contained within the cambium, and is of very 

 abnormal development. It contains a large number of bundles 

 developed from abnormal merismatic tissue. The vascular por- 

 tion consists of pitted vessels and tracheids. The parenchyma 

 contains starch, resin cells and calcium oxalate crystals. The 

 starch grains, both of this tissue and the cortex, are often 

 gelatinised by the heat to which the drug has been subjected. 



In the powdered drug there are but few intact resin cells, but 

 numerous globules of secretion that have been liberated 

 during the pulverisation. 



The diagnostic characters of powdered jalap root are : 



(a) The starch grains, many of which are gelatinised. 



(b) The secretion cells and the droplets of resinous emul- 



sion that have escaped from them. 



(c) The sclerenchymatous cells. 



(d) The rosette crystals of calcium oxalate. 



