194 TEANS ACTIONS AND PROCEEDINGS OF THE [Sess. LXiii, 



Specimen 4, Plate III., is, histologically, a rather inter- 

 esting type. It is an irregular fragment of 3 cm. in thick- 

 ness, and about 1 by 8 cm. in dimensions on the transverse 

 polished face. Only a small part of this area, measuring 3 

 by 2 cm., however, exhibits structure, but the minute detail 

 is very perfect. This particular part is distinguished by 

 its dark brown ferruginous tint, as contrasted with the dark 

 smoky tints merging into blue and grey of the bulk of the 

 section. At first sight it would appear, from certain appear- 

 ances in the cavities of the tracheie, that at the time of 

 silicification the fragment of wood was, to a large extent, 

 far gone in decay, permeated by fungal hyphfe which have 

 been fossilised in situ in the interior of the trachccf. I am 

 inclined to place a different interpretation on these peculiar 

 appearances, but of this more anon. 



The tree has been a deciduous one of moderate growth, 

 about nine rings per inch of radius ; the annual rings are 

 very distinctly demarcated by the difference in calibre, 

 as well as distribution of the various elements, as also by 

 peculiarities of tlie medullary rays. These last are not 

 very numerous, only about twenty-four on an average for 

 five millimetres. Their breadth is fairly uniform, averaging 

 •0321 mm., except at the junction of each annual ring, 

 when they broaden out laterally to twice or thrice their 

 average in other parts of their course ; even in the middle 

 of a year's ring this lateral broadening may be remarked. 

 In this peculiarity regarding the rays, it resembles some 

 Leguminos.'i- as also Cupulifera\ Their radial course is not 

 very continuous; starting as a single row of cells, one may 

 broaden out to the average extent, extend across a ring or 

 little more, and suddenly disappear opposite a trachea, from 

 the adjacent sides of which two new rays pass outwards. 

 This eccentricity, of course, renders the interradial spaces of 

 varied breadth ; the interval between adjacent rays may be 

 so great that there is room for two tangential rows of large 

 trachea; abreast; often, however, only one row, and fre- 

 quently the spaces are so narrow that the rays are deflected 

 outwards in passing tracheie. 



Annual Tiiiujs. — The average breadth is about 3*2 mm., 

 and the annual rings are demarcated in the same way 

 as in present-day trees. There is a highly porous .zone 



