940 PROFESSOR W. C. WILLIAMSON AND DR. D. H. SCOTT ON THE 
The Vegetative Stem. 
A specimen which appears to throw light on the structure of the stem of this plant 
in its vegetative region, has been described and figured in a previous memoir.* This 
specimen is a mere fragment, of which we know only the transverse section. It was 
obtained from the same source, the Foot-mine at Oldham, which has yielded some of 
the specimens of the strobilus itself. 
The primary wood is bluntly triquetrous, and appears to consist of a perfectly solid 
mass of traches. The details of its structure, so far as the transverse section can 
show, are absolutely identical with those of the xylem-strand in the axis of the 
strobilus.t 
Tn the vegetative specimen, however, the primary xylem is surrounded by a zone of 
secondary wood, 12-15 elements in thickness. The structure of this secondary wood 
agrees exactly with that of Sphenophyllum plurifoliatwm, except that the distinction 
between fascicular and interfascicular wood is somewhat less marked than in that 
species. 
Portions of the secondary cortex are also preserved ; the cortical cells are arranged 
in radial series, which generally correspond to those of the wood. At one place we 
could distinguish three zones of cortical tissue.{ It is probable that we have in this 
stem, as in the species of Sphenophyllum above described, a succession of deep-seated 
peridermal layers. 
So far as the evidence extends, there is every reason to suppose that this specimen 
is a stem of the same plant as that to which the strobilus belonged. It differs from 
the axis of the latter just in those points (secondary thickening, and loss of primary 
cortex) in which we should expect a persistent vegetative stem to differ from the 
short-lived axis of a fructification. The primary structure of the two, so far as it can 
be compared, is identical. 
Now the anatomy of the vegetative specimen is that of a Sphenophyllum, though 
somewhat different from that of any of the species of which the structure has been 
previously described. This specimen thus established a presumption that “ Bowmanites 
Dawson” was the fructification of a Sphenophyllum, or of some closely allied plant. 
This presumption has now been raised to a certainty by M. ZEILLER’s observations. 
AFFINITIES. 
M. ZEILLER’s investigation of his fine specimens of the fructification of Spheno- 
phyllum cunerfolium has established the following facts: the bracts of each verticil 
* Wittamson, “ Organization,” Part XVIL., Plate 15, tig. 19. 
+ Compare WixLiamson, loc. cit., Part XVII., Plate 15, fig. 19, with Part V., Plate 5, fig. 29, or with 
Part XVIII, Plate 25, fig. 1. 
$ Not clearly shown in the figure cited. 
