OF LOWER GREENS AST) PLANTS. 181 



Species founded on woody branch not less than 5 cm. in 

 diameter when alive, now decorticated ; pith present. 



HORIZON. Lower Greensand. 



LOCALITY. Luccorab Chine, Isle of Wight. 



TYPE. Woody branch, no. V. 13195 and slides V. 13195 a to 

 V. 13195 c cut from it; British Museum (Nat. Hist.); also 

 slides SD. , d, &/, Stopes coll., cut from the same block. 



FINDER. M. C. Stopes, 1912. 



DESCRIPTION. The type and only specimen is a portion of 

 a branch 3*5 cm. in diameter, of w r hich a length of 6 cm. is well 

 petrified in a dark siliceous medium. Externally the decorti- 

 cated woody texture shows through fragmentary remains of the 

 coarsely granular matrix. As the wood is entirely decorticated, 

 it is not certain whether it represents a small lateral branch or 

 the core of an older stem. As the pith is excentric to the 

 present diameter, it indicates that the branch when living could 

 not have been less than 5 cm. in diameter. 



TOPOGRAPHY OF THE STEM. Pith is preserved in the centre of 

 the axis, and is about -6 mm. in diameter. It is torn away 

 from the surrounding primary wood, and the outer cells are 

 mostly destroyed. The main mass of the pith is composed of 

 two types of cells, viz. roundish cells with somewhat thickened 

 walls and also very much thickened stone-cells. 



The primary wood is grouped in inconspicuous bundles. 



The secondary wood shows well-marked growth-rings, a few 

 of which are double or " composite." The wood is rather 

 irregular in texture (text-fig. 51), and has numerous resin- 

 containing parenchyma-cells scattered all through its extent. 

 The rings consist of from 25-80 tracheids in radial series, the 

 larger rings measuring about 2 mm. in extent, the number of 

 specially narrow autumn elements varying from 4-10. Normal 

 resin-canals are entirely absent ; one or two traumatic canals 

 lie near a closed-over wound or branch exit. 



Medullary rays in transverse section are fairly numerous and 

 conspicuous. They are uniseriate, and lie from 1 to 12, principally 

 2-5, tracheids distant. The rays are 1-10 cells high, the 

 great majority being 2 cells high. While uniseriate rays are 

 the rule, here and there a small ray is partly biseriate, but the 

 elements are all alike and the rays undiff'erentiated. 



The section shows a small branch being given off. 



