164 Mr. Thomas Hick on 



The pith, so far as it is preserved, is made up of thin- 

 walled cells, elongated longitudinally, which are usually 

 narrower at the periphery than towards the centre. In some 

 cases a few larger cells, with carbonaceous contents, are 

 intermingled with the smaller peripheral ones, but these are 

 not present in the transverse sections figured. They have 

 a close resemblance to the cells which occupy the middle of 

 the inner zone of the cortex. The pith cells at the nodes 

 are rounded, and may or may not contain accumulations of 

 carbonaceous matter. 



The vascular elements which cling to the sides of the 

 carinal canals are not all of one kind. Some of them are 

 clearly annular, and others are spiral ; but occasionally 

 reticulated ones are also present, a state of things which 

 may occur in Equisetum. 



Longitudinal views of the phloem are much rarer and 

 still more fragmentary than those through the xylem, and 

 at present I can only say that the phloem elements appear 

 to be narrow elongated structures. 



Coming to the cortex, it may be said with some degree 

 of confidence that the larger elements of the inner zone, 

 though often considerably elongated, are nevertheless 

 cellular. They are, in fact, several times as long as broad, 

 they have oblique or square ends, and stand in vertical 

 rows. But there are no signs of thickening or sculpturing 

 of the walls. The carbonaceous contents are usually 

 retracted from the side walls, and at the ends sometimes 

 take the expanded, trumpet-like form, characteristic of 

 the contents of some sieve-tubes. This, and the arrangement 

 in vertical rows, suggests that they formed conducting 

 channels, but the nature of the conducted materials cannot 

 at present be determined. 



With respect to the outer zone of the cortex, little has 

 been made out in the longitudinal view beyond the fact that 

 the thick-walled elements seem to be more or less fibrous 



