ANATOMY OF GL'AVLLE I79 



Furthermore the cutting t)ut of bast in oldcM- steins interferes 

 with the usefuhiess of the method, though it must be said 

 that, in practice, this is of little importance since such large 

 plants will not be grown. Probably, when rightly understood, 

 the method suggested by Ross will serve well enough, 

 especially when checkeci by the use of other marks. 



As shown by the same author, bundles of hard fibers 

 occur from time to time, alternating with secondary resin 

 canals and sie\e tissue, in which these canals arise. These 

 occur also in the pith of the stems of the inflorescence. It 

 would appear from Ross' account that these mechanical ele- 

 ments in the pith are confined to the peduncle and its branches, 

 but this is not the case. Bundles of fibers, exactly similar to 

 the cortical bast fibers, appear within the pith just inside 

 the primary wood in ordinary stems, sometimes somewhat 

 removed, and separated from the wood by a few' small pith 

 cells, but more usually juxtaposed. After some degree of 

 secondary thickening, the similar appearance of the mechan- 

 ical elements of the wood proper and those of the pith 

 prevents their ready detection. It is these fibers which run 

 up into the peduncle, and, spreading around the vvood 

 bundles, join the cortical bast fibers and so close the bundle, 

 thus producing a ^'ery stiff though slender flower stalk. The 

 same structure may be seen in the annuals abo\-e mentioned, 

 but it is further elaborated in them. 



A further peculiarity of the pith is its local induration, 

 by thickening of the cell-walls in irrigated plants, a circum- 

 stance which may contribute to the strength of the stem, 

 which is remarkably more rigid than that of a field plant. 



Among other details noted by Dr. Ross, we shall men- 

 tion further only the slowness with which the bark is formed 

 and the persistence of the cortical structure. Even with the 

 formation of inner periderm, th^^ cutting out of tissues is not 

 rapid. 7 he cork is, howe\er, visible quite close to the grow- 

 ing point, the distance being related to the rate of growth. 



