12 Weiss, XenopJiyton radiailosiun (Hick). 



organs visible. In some places the outer cortex is only- 

 two or three cells in thickness, and at some points only 

 one layer of cells is visible, but here it would appear that 

 the outer layers have become destroyed, probablj^ after 

 the death of the root. 



The middle cortex, which is so generally absent or 

 defective in stigmarian rootlets, is, in the specimen under 

 consideration, represented by a massive and well-preserved 

 tissue of the character usually found in Lepidophloios 

 fuliginosiis, and also seen in XenopJiyton. The more or 

 less elongated cells {Plate XIII., Fig. 4) form a dense felted 

 mass, evidently of greater strength than is usual in the 

 middle cortex of stigmarian rootlets, if, indeed, the latter 

 possessed in all cases a definite middle cortex. It is 

 quite conceivable that in many stigmarian rootlets there 

 may have been a definite space between the outer and 

 inner cortex, bridged over only at one side by a strand of 

 cells such as we find in the roots of A^^7^j. Such roots 

 are figured by Williamson." On the other hand, some 

 rootlets with well-preserved middle cortex have been 

 figured by Williamson,-;- Hooker ('48), and Goeppert 

 ('41), but in none of these cases was the tissue of the same 

 character as that under consideration. It seems probable 

 that the stigmarian rootlets, representing as they do the 

 roots of widely different plants, possessed some diversity 

 in structure, and the presence or absence of a middle 

 cortex, and the structure of this layer when present, would 

 seem to have been one of the variable features of these 

 roots. The presence and the nature of the middle cortex 

 in the rootlet under consideration, and its excellent pre- 

 servation depending, as it must largely do, upon the 

 nature of its cells, point to a close association of this 



* Williamson, W. C. ('87) Plate XIII., Fig. 79. 

 + Williamson, W. C. ('81) Plate LIIL, Fig. 15. 



