XVIIl] BOTHRODENDRON 261 



chymatous cells, c'. The larger section shown in fig. 215, D, 

 was cut from a specimen from Dulesgate of which the smooth 

 surface exhibits the characteristic leaf-scars of Bothrodendron. 

 The section measures 3 cm. in its longest diameter and the 

 stele has a breadth of 3 mm. The outer cortex has a smooth 

 surface and is composed of rather thick-walled cells succeeded 

 by a zone of secondary elements. The middle cortex has 

 disappeared and the space is partially occupied by Stigmarian 

 rootlets, s, and crushed patches of cortical tissue. The position 

 of a leaf-scar is seen at a ; this is more clearly shown in the 

 enlarged drawing fig. E. 



In his account of Lepidodendron inundum, Williamson^ de- 

 scribed a section in which the primary wood is surrounded 

 by a considerable thickness of secondary xylem; a diagram of 

 this is shown in fig. 215, C. An examination of the section led 

 me to compare the structure of the outer cortical cells, charac- 

 terised by radial rows of tangentially elongated elements, with 

 the outer cortex of Stigmaria. It has recently been shown by 

 Weiss '^ that this and other similar sections present several 

 points of agreement with Stigmaria, particularly with Stigmaria 

 Brardi as described by Renault. At s in fig. 215, C, a vascular 

 strand is seen passing through the outer cortex ; this is almost 

 certainly the bundle of a rootlet : in the sections described by 

 Weiss rootlets are shown in a similar position. The chief 

 anatomical features of the Stigmaria-like organs of Bothro- 

 dendron are : — the considerable development of secondary xylem, 

 the structure of the outer cortex, which is practically identical 

 with that of Stigmaria ficoides, and the association of groups of 

 short transfusion tracheids with the bundles of the rootlets. It 

 is very probable that the absence of secondary xylem in the 

 vegetative shoots of Bothrodendron is merely an accident and 

 not a real distinction between the aerial and subterranean 

 branches of the plant ; a supposition rendered probable by the 

 occurrence of secondary xylem in the axis of the cone described 

 by Watson. As Weiss points out, there are certain differences 

 between the true Stigmaria and the corresponding organ of 

 Bothrodendron; the secondary xylem in Bothrodendron is not 



1 Williamson (89) A. ^ Weiss, F. E. (08). 



