224 DESCRIPTIVE CATALOGUE 



Traeheids small, up to about 28 ft in diameter, even the spring 

 elements rather thick-walled and very much rounded off at the 

 corners, leaving considerable intercellular spaces between the 

 tracheids. Bordered pits in one row, nearly circular but slightly 

 flattened where they are adjacent in short chains of three to a 

 dozen disposed in the thicker parts of the tracheids, which appear 

 to be locally wider and more constricted in different regions. 

 Wood-parenchyma is scattered through the wood. Medullary 

 rays all uniseriate, chiefly 2-4, up to 8 tracheids distant, 

 principally low, i. e. 2-4 cells high. Ray-cells uniform, walls 

 thickened but smooth, abietinean pitting absent, end-walls at an 

 angle. Single large pits per tracheid-field, with wide-open oval 

 pores placed at an angle, and with nearly round wide borders. 



HORIZON. Woburn Sands, Lower Greenland. 



LOCALITY. Woburn. Bedfordshire. 



TYPK. An axis, which may be the core of a larger trunk, 

 no. V. 13191, and slides V. 13191 a-d cut from it in I'.Hi'; 

 British Museum (Nat. Hist.). 



DESCRIPTION. The specimen at present measures 6x3 cm. in 

 diameter and is 13 cm. long. It is irregularly split, and may be 

 the core of a large trunk or may bo a smaller branch : in any 

 case, it could not be less than 8 cm. in diameter when alive, as 

 is indicated by the present position of the centre of the stem. 

 Externally the specimen is free of matrix, and shows the partly 

 weathered and partly freshly broken texture of the secondary 

 wood split in various directions. The wood is evidently drift 

 wood and has several teredo-borings. The petrifying medium 

 is close and hard, externally weathered to a whitish cream, and 

 internally a rich brown colour. The preservation is locally very 

 good, though the pith and primary wood are obliterated. 



TOPOGRAPHY OF THE STEM. (Secondary wood only is preserved, 

 the pith and primary wood at the centre of the axis being 

 entirely decayed. Over 30 growth- rings are preserved, but 

 are not very sharply marked in the texture of the wood, 

 as there are only 3 or 4 rows of autumn elements the walla 

 of which are not greatly thickened, and even the last row of 

 autumn wood does not sho\v any great radial compression. 

 In transverse section the rings show well ( I'l. XXI, fig. 1) 

 because of the accumulations of blackened and carbonised 

 granules in the first-formed spring wood. The wood is uniformly 



