368 ERNEST WARREN. 



The fossil wood has a specific gravity of 1*43, the increase 

 being doubtless due to the infiltration of mineral matter. 

 Fine compact grain with dull surface. Pores variable in size 

 and distribution. A narrow area poor in vessels occurs as a 

 kind of boundary between the somewhat faintly defined 

 annual rings. 



The pitted vessels with a variable diameter of 0'050- 

 0"156mm. are frequently solitary, sometimes in pairs. There 

 may be small nests consisting of one or more pitted vessels^ 

 with a niimljer of smaller vessels ; these latter are scalariform 

 (PI. XXVI, fig. 16, sc), and have a diameter of about 

 0'025 mm. The number of pitted vessels is variable over 

 different areas; the average of a number of counts gave 12 

 to a square millimetre. 



Medullary rays exceedingly numerous, and in an uncon- 

 torted portion of the wood they are straight. They are 

 swollen in the middle where they consist of three or four cells 

 in thickness, and taper above and below into long ends. The 

 middle poi'tion consists of 15-25 cells in vertical height, and 

 they are there smaller than in the ends. In transverse section, 

 including both " ends " and " middles," there are 20-26 per 

 millimetre. Radial length of medullary cells 0'042-0'()73 nmi. 

 Vertical height of end cells about 0"046 mm. 



The wood fibres have a diameter of about 0*0182 mm. 



Communicating with the pitted vessel there are occasional 

 groups of several parenchymatous cells with walls having 

 large pits (fig. 16, p.c). 



The pitted vessels are frequently blocked up with masses of 

 laro-e irregularly rounded cells which constitute the thyloses 

 (fio-. lQ,th.). Neither in the recent wood nor in the fossil 

 wood are annual rings clearly marked, although zones of 

 more or less poreless wood do occur. 



The wood parenchyma in longitudinal section is seen to 

 consist of somewhat elongated cells arranged in vertical rows. 

 Thev do not appear to be definitely related to the vessels 

 (fig. 16, u'.p.). 



On the whole the structure of the fossil wood may be said 



