XLIV] PITYOXYLON 227 



medullary rays occur, the latter with horizontal resin-ducts. There 

 are no ray-tracheids. There is usually one circular or elliptical 

 pit in the field. A second species from the same locality, Pityoxylon 

 scituatense, differs only in some unimportant features from P. staten- 

 ense. These fossils differ from recent Pines as also from Picea, 

 Pseudotsuga, and Larix in the absence of ray-tracheids. In the 

 restriction of bordered pits to the tangential walls of the tracheids 

 of the summer-wood they agree with the soft Pines, but though 

 this character is generally lacking in hard Pines, Jeffrey and Chrys- 

 ler point out that in some haid Pines without pits on the tangential 

 walls of the tracheids of vegetative shoots the summer elements 

 of the cones have tangential pits. The occurrence of bordered 

 pits on the tangential walls of the late wood and the absence of ray- 

 tracheids are regarded by the authors of the species as ancestral 

 features. 



Pityoxylon protoscleropitys (Holden). 



A Middle Cretaceous species 1 from New Jersey, referred by 

 Miss Holden to Pinus, showing the following features : annual 

 rings well developed ; linear and fusiform medullary rays, hori- 

 zontal and vertical resin-canals, bordered pits uniseriate and scat- 

 tered on the radial walls of the tracheids ; none on the tangential 

 walls. Kims of Sanio are present. There are 1 2 pits in the 

 field with a lenticular pore and circular border; the other walls 

 of the ray cells are abundantly pitted. Ray-tracheids occur on 

 the margins of the medullary rays and rarely interspersed with the 

 parenchyma; their walls are denticulate as in recent hard Pines. 



The presence of horizontal tracheids in the medullary rays is 

 an important character: in Pityoxylon scituatensiformis (Bailey) 2 , 

 another Middle Cretaceous species, ray-tracheids are present but 

 they have smooth walls and are not met with in the first 10 15 

 rings of wood, whereas in P. protoscleropitys they occur even in the 

 wood of the first year. In this connexion the presence of ray- 

 tracheids in Pityoxylon eiggense is noteworthy at least if that species 

 is from a Jurassic source. Pityoxylon protoscleropitys is considered 

 by Miss Holden to be 'probably the earliest form with all the 

 characters of a modern hard Pine, yet retaining certain ancestral 



1 Holden (13 3 ). 2 Bailey (11). 



152 



