OF LOWER GREEXSAND PLANTS. 81 



The new Lower Greensand form, which, while it undoubtedly 

 belongs to this genus, yet differs essentially from P. extinctum, 

 makes it possible to diagnose the genus provisionally as given 

 above. 



Protopiceoxylon Edwards!, sp. nov. 

 [Plate III ; text-figs. 17-22.] 



Diagnosis. A. woody branch, 4'5 cm. in diameter, with 17 

 wood-rings. The vertically running resin-canals are only in 

 the autumn wood, and are present in every annual ring, and 

 scattered all round each in larger or smaller numbers, either 

 singly or in tangential series. Resin-canals are very small, 

 many with only 4-5 epithelium cells, which have thick walls 

 pierced by many pits, and are pointed or blunt at the ends 

 in tangential section. The pith is large, without stone-cells. 

 Primary xylem all apparently centrifugal. The secondary wood 

 has stout, very well-marked annual rings with exceedingly 

 thickened autumn wood. Spring tracheids up to 55 X 50 ^ in 

 diameter, with round, isolated, bordered pits in a single row on 

 the radial walls, the border of each pit being considerably less 

 than the diameter of the tracheid wall in which it lies. There 

 are a few pits on the tangential walls of the autumn wood. 

 Small quantities of resin-parenchyma are associated with the 

 resin-canals, but apparently it is absent elsewhere. The 

 medullary rays are all uniseriate, principally low, with very 

 much thickened walls showing characteristic " abietinean 

 pitting " and groups of 2-4 irregularly roundish pits per 

 tracheid-field in the radial walls. 

 HORIZON. Lower Greensand. 

 LOCALITY. Berwick Green, Sussex. 



TYPE. Petrified branch, V. 4859, and slides cut from it, 

 V. 4859 a to V. 4859 m in the British Museum (Nat. Hist.). 



DuscRiPirox. This species is founded on a single specimen, a 

 short length (about 5 cm.) of a branch 4'5 cm. in diameter. 

 The branch is decorticated and externally shows part of the 

 woody texture, and is partly embedded in the coarse granular 

 matrix. One end of the branch has been much weathered, and 

 the well-marked annual rings stand out in high relief. The 

 cut end of the specimen also shows very clearly the sharply 



G 



