262 DESCRIPTIVE CATALOGUE 



GENERAL DESCRIPTION. The large specimen, uow measuring 

 25 x 5 x 23 cm., is evidently part of a still larger woody trunk, 

 which, judging from the curve and direction of the growth- 

 rings, could not have been less than 30 cm. in diameter when 

 alive. The wood is evidently a drifted log, water worn and 

 teredo-bored before petrifaction. It is petrified in a close hard 

 medium, very slightly iron-stained, and the surface is clean 

 from matrix and shows the woody texture exceedingly well, 

 particularly in the radial splints (text-fig. 7fi). Secondary 

 wood alone is preserved, without any sign of phloem or bark, 

 and the wood is that of the outer wood-zones, probably formed 

 when the plant was many years old, as there is no sign of the 

 more abrupt curves of the limits of the central rings of growth. 



TOPOGRAPHY OY THE WOOD. The proportion of vessels to 

 wood-fibres and parenchyma is large, as can be seen in PI. XXVI, 

 figs. 1 & 2. The vessels are scattered singly, very close to each 

 other, often with only one fibre-tracheid or wood-parenchyma 

 cell between them, or with very small groups of these elements. 

 In several cases series of vessels may be adjacent. Wood- 

 parenchyma is small in quantity, and is scattered among the 

 small groups of fibres, and may or may not be adjacent to the 

 vessels. Growth-rings are clearly to be seen (PI. XXVI, fig. 1), 

 but the autumn zones are very narrow, and have little or no 

 effect on the distribution of the vessels. The whole zone 

 measures from about '5 up to 2'5 mm., and is therefore 

 narrow for the size of the whole trunk. 



Medullary rays are very numerous and uniseriale. I have 

 not detected any broader multiseriate rays, even in sections of 

 large area, so it is probable that they are entirely absent. The 

 rays consist of cells all very much alike, averaging from about 

 10-24 cells in vertical sequence. 



DETAILS OF THE ELEMENTS. The wood-vessels are now rather 

 crumpled in most cases, but were normally roughly circular or 

 squarish in transverse section. They average about 30-50 p. 

 in diameter, and are therefore small. The walls appear to have 

 been but slightly lignified. In longitudinal sections, however, 

 the pitttngs show up with remarkable frequency and beauty 

 of preservation. The main lengths of the vessels are per- 

 forated by innumerable, smull, oval, bordered pits (PI. XXVII, 

 fig. 1). lying between the vessels and the adjacent ray-cells 



