196 DESCRIPTIVE CATALOGUE 



DETAILS OF ELEMENTS. The great majority of the wood 

 traclieids have the size and character of the spring wood, 

 since the zone of autumn wood is narrow and the rings 

 of growth are wide. These tracheids measure about 30x40 

 up to 50 x 60 /i in transverse area ; their walls are not much 

 thickened and very little rounded at the corners. The autumn 

 wood, of which there is but a small quantity, consists of 

 elements with the same tangential diameter and about 

 half the radial diameter of the spring wood, i. e. about 

 30x12 to 40x15^; the walls are about 5-7 /i thick in the 

 last-formed autumn wood. In transverse section the larm>- 

 bordered pits are very noticeable ; due apparently to a pecu- 

 liarity of petrifaction or of decay before petrifaction, the round 

 border is blown up, like a halt' balloon. This appearance is 

 also seen in the tangential longitudinal sections (test-tig. 57). 



In radial section (text-tig. 50) the pits are seen to lit- in 

 a single row, generally separated from each other by some 

 distance. The pits in the tangential walls of the autumn 

 tracheids can be seen in transverse section in several places. 

 Wood-parenchyma cells of large si/e, with thin walls and, as a 

 rule, with blackened resinous contents, are apparent through- 

 out the wood. In transverse diameter they are as large or even 

 larger than the tracheids. In radial section the cross-wall 

 slightly constricts the element; this is not the case in the 

 tangential section, where the walls also run transversely (text- 

 tigs. 56 & 57). The end-cells of a cell-row have pointed termi- 

 nations which tit into the tracheids. I have not observed any 

 special pitting in the walls. Kesin-canah and specialised resin- 

 tracheids are absent. 



T\\euniseriate and multiserlate medullary rays&re not different 

 in kind, and the same ray may be uniseriate for some part of its 

 vertical extension, then biseriate, and then again uniseriato and 

 then again biseriate. Much variety in the build of the rays can 

 be seen in PI. XVIII, fig. 2. The end-walls of the ray-cells are 

 slightly sloped or curved ; the radial extension of a ray-cell 

 equals from 2 to 8 or 9 tracheids. The tangential diameter 

 of the ray-cells is rather less than or equal to the adjacent 

 tracheids. The cells all have slightly thickened walls, but 

 the petrifaction does not show whether they have any true 

 ' abietineaii pitting " or not. The only pitting visible is the 



