PITYOXYLON 349 



46. P. Peali, Knowlton 



" Transverse. This section shows the late fall and early spring wood. The 

 contrast in the thickness of the cells makes a very clearly marked ring. 

 This ring of growth was very broad, being in some cases fully 10 mm. 

 The medullary rays show in this section also as long, slender cells. 



"Radial. The specimens are in a fine state of preservation. The cells of 

 the spring and summer wood are very broad and marked with a single 

 series of large, scattered, bordered pits. The medullary rays are prom- 

 inent. They are composed of very long cells, each of which is marked 

 usually by 2 or 3 small, oblong, or nearly circular bordered pits the 

 width of each wood cell. 



" Tangential. The medullary rays are arranged in a single series of from 2 

 to occasionally 20 superimposed cells. The resin tubes occurring in 

 the midst of a medullary ray are quite numerous. There are no recog- 

 nizable pits or markings on the tangential walls of the wood cells" 

 (Knowlton). 



Material silicified. 



Miocene of the upper Gallatin Basin, Montana (Knowlton). 



47. P. chasense, Penh. 



Transverse. Tracheids chiefly in regular radial rows, very variable in size, 

 squarish, about 44 x 44 //, broad; the walls 12.5 /j. thick. Medullary 

 rays numerous, chiefly i cell wide, occasionally 2-3 seriate. Growth 

 rings wholly wanting. Resin cells and resin canals not represented. 



Radial. Ray cells all of one kind ; straight, equal to 2-4 tracheids ; the 

 upper and lower walls thin and not pitted ; the terminal walls thin, not 

 pitted, straight or curved ; the structure of the lateral walls not deter- 

 minable, but the pits are probably round. Bordered pits in 1-3 rows, 

 chiefly 2 rows, round or hexagonal, 12.5 /j. broad, the orifice probably 

 round. 



Tangential. Rays of two kinds: (i) i-seriate rays, the cells oblong, 25 p. 

 broad, often 2-seriate in part ; and (2) fusiform rays, the terminals linear 

 and of the structure of the i -seriate rays ; the central tract very broad, 

 nearly round ; the cells large, thin-walled, irregular, and inclosing a 

 small, central resin passage with large epithelium cells. 



Material silicified. Specimens represented by small fragments of stem. 

 From the Chase Formation (Permian) at Coon Creek, Chase County, 

 Kansas (Prosser). 



48. * * P. statenense, Jeff, and Chrys. 



Transverse. Growth rings variable, chiefly narrow but usually well defined ; 

 summer wood very variable, of the narrower rings 1-5, but of the 

 broader rings many tracheids thick and constituting upwards of two 

 thirds the total thickness ; transition from the spring wood somewhat 

 abrupt; the broader growth rings sometimes showing 2 zones of 

 summer wood. Tracheids round-hexagonal or rectangular, rather 



