6 1 8 
Notes. 
with the secondary wood. At two or more points in the transverse 
section a pair of these small bundles was observed just entering the 
zone of secondary wood. At each of these points there was another 
bundle a little way to the interior, apparently a ‘ faisceau rdparateur ’ 
about to replace the outgoing strands. At another place a strand 
was observed passing out through a large ray of the secondary wood. 
The primary xylem-strands show in most cases a very distinct 
mesarch structure. The smallest elements are near the middle of 
the strand, and are shown by the longitudinal sections to be 
spirally thickened, while the surrounding tracheides are reticulate. 
Anastomosis appears to occur frequently among the primary 
xylem-strands. 
The secondary wood, which is exquisitely preserved, though only 
present in small quantity, is of the type characterizing the subgenus 
Pissadendron 1 ( Pitus of Witham, Palaeoxylon of Brongniart). The 
numerous medullary rays attain a great height, and are commonly 
four cells in thickness, though small uniseriate rays also occur. 
Towards the pith the rays are much dilated, and the woody wedges 
correspondingly restricted. 
The pitting of the secondary tracheides is preserved with astonishing 
perfection, and is of the Araucarian type; there are usually from three 
to five rows of the hexagonal pits, each with a narrow, horizontal, or 
inclined pore, on the radial wall of each tracheide. Tangential pits 
also occur in places. The innermost secondary tracheides show 
a spiral thickening, which, however, as in the tracheides of the Yew, 
appears to co-exist with a pitted structure. 
The organization of this stem is, so far as I am aware, quite unique. 
The numerous small circum-medullary xylem-strands, for the most 
part independent of the zone of centrifugal wood, appear to be without 
any near parallel among recent or fossil Gymnosperms as at present 
investigated. 
Yet I believe that the fossil in question is one that has long been 
known. It will be remembered that Lennel Braes, on the Tweed, from 
which Mr. Kidstons specimen comes, was one of Witham’s localities, 
whence he obtained specimens of his Pitus antiqua 2 . Witham’s plant 
agrees so well with Mr. Kidston’s specimen, as shown by a comparison 
1 Kraus, in Schimper, loc. cit, p. 384. 
2 Witham of Lartington, Internal Structure of Fossil Vegetables, Edinburgh, 
1833, pp. 23, 37, 71. 
