CHAP- n. 



EXOGESfOrS STEMS. 



/ / 



Coniferae; tdi^ place being sapplaed by siaeli woody tis&ue as 

 has bem abteadk described at p. 19. But tbe zones of wood 

 are a^arated by a layer of oelliilax sabstaiiee i^iembling that 

 of the pith, and o^n as tbick as the ^xmes tlieiiiselves. Thk 

 stmctare is r^resented by Adolphe Brongmart. in tbe 16di 

 Tofanne of tbe Annales des Sc^iaces. 



Mt &ieDd Mr, Griffith has beaolifiallT iflnsti^ted tbe stme- 

 tune of a plant called Riytoenaie {fig, 34.1,10 Wallieh's Pkatae 

 Asiatics, toL iiL 1. 1216. In tbis carious production tbe wood 

 consists oi plates containing vessels and woody tissue, baring 

 DO eonnectioii with each other, and separated at very eans- 

 derable intervals by a large mass of {MX^endix'Qffltioas eelbi^ 

 tksoe filled with vasifonu tfene, and rejH«senting mednlaiy 

 rays.* Wbai tbe stem is dry, tbe woodk^btes separate frowa 

 die odiar t^oe, in which tbev finallv lie loosse. 



S4 



\^^ s^m^.y 



In Nepoidies distillaitoria tbe pith ccmtains a grtat qoantit^- 

 of ^lal vessels ; tbe jdaoe of tbe medulkiT sheath is occn- 

 jHed by a deep and dense layer of woody tis5^le, in which no 

 vessdts, or scarcely any, are discoverable ; tb«¥ are uo me- 

 dnBaxy rays; tbe wood has no CMicaatric zcaaes : between the 

 bark and the wood is interposed a dii«i layer of ceDukr tisaie, 

 in wfaicb an immense qoantity df Tsay ^ige ^iral vessels is 

 formed; on the outside <rf this iayar is a thinner coating of 



* It i»ill be aeem tAat tdae triew I bow tate ^die aoailoiries of tbe parts 

 ai dieinmk oiVhyuxreat is verr ^ifferEatfixm tli^ in tie first etfitkni of 

 thkwortu 



