THE INTERNAL STRUCTURE OF SIGILLARIA ELEGANS. 545 
The cells of the innermost layer of cortical tissue lining this zone consist of 
smaller cells, roughly tabular in transverse section, and have very much the appearance 
of an endodermis (PI. II. fig. 26, e; Pl. I. fig. 27, e). 
Within the clear zone is a central mass of xylem (PI. III. fig. 25,4; Pl. I. fig. 27, 4), 
surrounded by a fairly stout zone of comparatively large thin-walled cells, separated from 
the xylem by a dark line of disorganised material (Pl. I. fig. 27, h). The xylem is too 
badly preserved for detailed description, but it is quite clear its development is 
centripetal. The smallest elements are at the periphery, and there is a gradual increase 
in size towards the centre. ‘There is no trace of any secondary thickening. 
The zone of thin-walled tissue surrounding the xylem possibly represents the so- 
ealled phloem of Lepidophiowws, but the preservation is so imperfect that a definite 
decision as to its true nature is not permissible. 
Remarks.—The structure of Sigillaria elegans, Brongt., is very similar to that of 
Sigillaria elongata, Brongt., the only other ribbed Sigilaria of which any detailed 
account of the structure has been given, but the short abstract of his paper given by 
Professor C. Ec. BerTRAND scarcely enables one to make a critical comparison between the 
structure of the two species.* He has, however, very kindly favoured me with some 
photographs of his specimen, and the general agreement in structure between the two 
plants is very striking. 
They both have a continuous circle of primary wood, with a distinct corona. In 
the Hardinghen specimen the projecting teeth of the protoxylem are pointed, while in 
the Yorkshire example they are rounded and contain a greater number of elements. 
The secondary xylem seems to offer no special point of difference. 
On my specimen the leaf traces rise as a single strand directly from the base of the 
furrows of the primary xylem, and they may differ somewhat in their mode of origin 
from those described by Professor Berrranp;t but until the full description of the 
Hardinghen specimen is published, it is undesirable to institute any critical comparison 
between the anatomy of Srgillaria elongata and Sigillaria elegans. 
In comparing the organisation of the various species of Sigillaria of which the 
structure has been described, one might be inclined to think that in the genus there 
were two types of structure; this, however, is not so. If one takes the Sigidlaria 
~Menardi described by Broneniart, with its isolated strands of primary xylem, and 
Sigillaria elongata or Sigillaria elegans, with their continuous circle of primary wood 
and prominent corona, they at first sight look very distinct. But in Sigillaria 
spimulosa, which normally is supposed to possess the same type of structure as Sigillaria 
Menard, Soums-Lavpacu has pointed out that the separate bundles of primary wood 
Sometimes coalesce, and in part form a continuous ring.{ This character of the 
Goalescence of the primary bundles of Stgillaria is also well seen in the figures of 
Sigillaria spinulosa given by Dr Scorr.§ In Sigillaria xylina, Renault, the same 
* Annals of Botany, vol. xiii. p. 607, 1899. + Loc. cit., p. 608. t Fossil Botany, English ed., p. 252, fig, 29, 1891. 
§ Studies in Fossil Botany, p. 201, figs. 77-78, 1900. 
