OF LOWER GKEENSAND PLANTS. 229 



borders. Primary wood all centrifugal, protoxylem-groups 

 large, elements spiral and scalariform. In one pith, large, 

 very thick-walled stone-cells are mingled with the ground- 

 tissue. 



HORIZON. Lower Green sand. 



LOCALITY. Luccomb Chine, I. of Wight. 



TYPE. Small decorticated branch, no. V. 13194 and slides 

 Y. 13194 a-c cut from it; British Museum (Nat, Hist.), and 

 slides SE a-c Stopes Coll. 



FINDER. M. C. Stopes, 1912. 



DESCRIPTION. The species is founded on a specimen of a 

 branch, 2'5 cm. in diameter, which is well petrified in a dark 

 brown silicified medium. The specimen is embedded in the 

 coarse granular matrix characteristic of the Luccomb Chine 

 deposit. 



TOPOGRAPHY OF THE STEM. Growth-rings are well marked and 

 very variable in thickness, a few being composite. 



The pith is about '6 mm. in diameter, circular, with five main 

 projections duo to the grouping of the bundles of primary wood 

 in five main groups. The cells of the pith are rounded, and all 

 arc thick-walled ; among the ordinary cells are large, excessively 

 thickened stone-cells (text-fig. 65,,?.). 



The primary wood forms small groups, the protoxylems seem 

 endarch, and no centripetal xylem has been recognised. The 

 secondary wood forms normal rings of solid wood, in which the 

 (jroiutli-rincjs tend to be composite. The wood-elements are 

 small, rounded at the corners, and adjacent elements lie on 

 alternating tangents, so as to fit into each other. Wood-paren- 

 cliyma containing resin does occur, though it is very scanty. In 

 transverse section the large number of dark elements in the 

 wood are due to carbonised granules, scattered irrespective of 

 arrangement, through the tracheids. In radial sections the 

 number of elements showing transverse walls, and thus proving 

 themselves to be parenchyma, is very small, which is charac- 

 teristic of plants of Phyllodadus- affinity, where it may be absent 

 altogether (see Gothan, 1908 A & 1907). Resin-canals are 

 absent. 



Medullary rays are all uniseriate, from 2-1 6 tracheids distant, 

 the commonest being from 6-9 tracheids distant. They are 

 low, from 1-10 cells high, the greater number being 2-4 cells 



