342 DR D. H. SCOTT ON THE 



state (see phot. 3) ; the main stem shows nothing outside the wood, and probably not 

 the full thickness of that, but the transverse sections also contain a detached fragment 

 which has the bark attached, though in a poor state of preservation. The main piece is 

 fairly well preserved, but in places the tissues appear to have suffered from maceration 

 before petrifaction took place. The most important region — the zone immediately 

 surrounding the pith — is a good deal damaged, but the chief features of its structure 

 are sufficiently plain, as the figures show. The pith, 13-15 mm. in diameter, has a very 

 characteristic appearance, owing to the presence of conspicuous masses of dark-coloured 

 cells, much resembling the ' sclerotic nests ' in the pith of Lyginodendron Old- 

 hamium * (see phots. 3 and 4). The nests here consist of rather thick-walled cells, 

 containing carbonaceous matter, which may probably have been derived from the 

 disorganised inner layers of a cell- wall originally much thicker than it at present 

 appears. In the middle of each nest there is a small irregular group of very dark 

 cells ; the more peripheral elements of the nest are squarish cells, arranged in series 

 radiating in all directions from the central group. These radial series are continued 

 out into the surrounding thin-walled pith, and are no doubt the result of growth and 

 cell-division subsequent to the first origin of the sclerotic nest. Such a structure is 

 commonly met with in recent plants, around groups of hard tissue differentiated in the 

 midst of an actively growing parenchymatous matrix. Similar cell-divisions occur 

 around the sclerotic nests of Lyginodendron, but not to the same extent as in the 

 present species. The general resemblance in the pith of the two plants is sufficiently 

 striking. 



The most important point, however, is the presence of a number of primary xyl em- 

 strands around the pith, adjoining the inner edge of the secondary wood. The bundles are 

 small compared with the size of the pith, though some of them reach a diameter of about 

 75 mm. (see PL IV. fig. 8). The larger strands are just entering the w T ood ; those which 

 remain at the periphery of the pith are smaller (see fig. 9). It appears, therefore, that 

 here, as in C. fascicularis, the strand attained its maximum size just before passing out 

 towards a leaf. As would be expected from the large dimensions of the pith, the xylem- 

 strands are numerous ; I was able, in spite of the imperfect preservation, to count seven- 

 teen strands which were clear enough for the position of the protoxylem to be recog- 

 nised. No doubt there were others besides, too obscure to be identified. In parts of 

 the periphery of the pith the primary xylem appears to be almost continuous, for the 

 inner edge of the wood is here formed of irregularly arranged tracheides, larger than 

 those of the secondary zone. This lateral confluence of the primary xylem-groups, 

 though not amounting to continuity all round the pith, recalls the structure found by 

 Count Solms-Laubach in Calamopitys annidaris.f The primary strands of C. beiner- 

 tianus bear a strong resemblance to those of C. fascicularis, as is evident if we compare 

 the large outgoing xylem-bundle shown in fig. 8 with the corresponding large strands 



* Williamson and Scott, loc. cit., p. 717 ; PI. 18, phots. 1 and 4 ; PI. 21, fig. 1. 

 t Loc. cit., p. 74. 



