22 



PHARMACEUTICAL BOTANY 



Underground Stems. — A rhizome is a creeping underground stem, 

 more or less scaly, sending off roots from its lower surface and stems 

 from [its upper. The rhizome grows horizontally, vertically or ob- 

 liquely, bearing a terminal bud at its tip. Its upper surface is marked 

 with the scars of the bases of aerial stems of previous years. 



The TxiBER is a short and excessively thickened underground stem, 

 borne usually at the end of a slender, creeping branch, and having 

 numerous eyes or buds. Ex.: Tubers of the Potato, Aconite, and 

 Jalap. 



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Fig. is. Fig. i6. 



Fig. 15. — Photomicrograph of cross-section of very young cornstalk, where the 

 procambium strands have just gone over into vascular bundles. For comparison 

 with Fig. 16. (From Steiens.) 



Fig. 16. — Photomicrograph of cross-section of cornstalk somewhat older than 

 in Fig. 15. Compare with Fig. 15, and notice that the number of vascular bundles is 

 approximately the same in both, and the number of cells in the fundamental tissue 

 is approximately the same. Growth in Fig. 16 has been accomplished by the enlarge- 

 ment of the cells already present in Fig. 15. a, Epidermis; b, cortex andpericycle; 

 c, c, fundamental or ground tissue corresponding to pith and medullary rays with 

 vascular bundles interspersed through it. (From Steiens.) 



The CORM is an underground stem excessively thickened and solid 

 and characterized by the production of buds from the centre of the 

 upper surface and rootlets from the lower surface. 



A BULB is a very short and scaly stem, producing roots from the 

 lower face and leaves from the upper. 



TuNiCATED BULBS are completely covered by broad scales which 

 form concentric coatings. Ex.: Onion, Squill, Daffodil. 



