234 CONIFERAIES [CH. 



Protopiceoxylon Edwardsi Stopes. 



Founded on a branch from the Lower Greensan,d of Sussex, 

 showing 17 annual rings, having the following characters^: a large 

 pith nearly 3 mm. in diameter composed of parenchyma without 

 stone-cells; tracheids with usually one row of circular bordered 

 pits; vertical canals in the summer- wood and associated with 

 a small amount of resiniferous parenchyma; medullary rays 

 uniseriate, with Abietineous pitting and 2 — 4 more or less circular 

 pits in the field. The small size of the resin-canals is a character- 

 istic feature, also their thick- walled pitted epithelial cells (fig. 729). 

 The species differs from Gothan's P. exstinctum in the smaller 

 diameter of the canals, the absence of traumatic horizontal canals, 

 and in the greater number of the vertical secretory passages. 



IX. WOODWORTHIA. Jeffrey. 



Woodworthia arizonica Jeffrey. This genus^ is founded on 

 specimens from the Triassic petrified forest of Arizona character- 

 ised by the occurrence of short shoots in the secondary wood com- 

 parable with those in the stem of Armicariofitys. In the type- 

 specimen the annual rings are not very clearly defined : the pitting 

 on the tracheids is definitely Araucarian. The medullary rays 

 are uniseriate, 2 — 9 cells deep : they appear to have pits only on 

 the lateral walls. 



On the surface of the wood are several small scars and a few 

 larger ones, the former representing short shoots subtended by a 

 leaf-trace ; the shoots are not infrequently branched as they pass 

 through the secondary xylem, a feature recorded also in Ginkgo^. 

 Jeffrey describes the short shoots as having a limited existence 

 and disappearing in the wood at a comparatively short distance 

 from the pith ; they have no rings of growth, a character associated 

 with short-lived leaf-spurs in recent species but a feature in which 

 they differ from those of Ginkgo. The leaf-traces subtending the 

 short shoots, in contrast to those of Araucaria, are not persistent 

 throughout the secondary wood. Jeffrey regards this fact as an 

 argument against the view that the persistence of the traces in 

 Araucaria is a primitive character ; but it is worthy of note that 



1 Stopes (15) p. 81, PI. HI. text-figs. 17—22. 



- Jeffrey (10^), Pis. xxxi., xxxii. 3 Tupper (11). 



