60 Scientific Proceedimis, Royal Dublin Society, 



length is If to 3 times the breadth. Short resin cells are found in wood, tending 

 to form traumatic resin canals. The end walls of the resin cells are thin and 

 unpitted (PI. Ill, iig. 7). 



Uniseriate medullary rays, only, are present, 2-20 cells high, each cell being 

 20-24/.( in height. The horizontal and tangential walls are unpitted. The pits 

 on the radial or lateral walls ai-e (PI. Ill, figs. 8, 9, 10, 11) usually in one, 

 occasionally in two horizontal rows. The pits, 1-4 in the field, appear simple 

 with oval pore, horizontally directed. They are ll-14|t in length and 5-8jU in 

 breadth. At 712 feet the pits (PI. Ill, fig. 11) were found to be bordered, so that 

 the simple pits are probably due to bad preservation. The arrangement of the 

 pits in the ray cells is very similar to that in S. gigantea, in which, however, the 

 pits are always bordered. In the fossil and in S. gigantea pores which are slightly 

 oblique may occasionally be seen, and occasionally 4-5 pits in two rows in the 

 field occur. 



In 8. sempervirens, in common with previous observers, we find two horizontal 

 rows of bordered pits with oblique pore in the cross-field is the normal 

 arrangement. 



The identification of the wood of living and fossil Conifers has for the past 

 seventy years been the subject of much investigation. The similarity in structure 

 in species which are far apart, judged by their external features, and the amount 

 of variation whicli may occur in any one species, render the task difficult in the 

 case of some living, but more so iu that of fossil Conifers. 



Recognizing the fact that leaf impressions and wood are hardly ever found 

 together in the same deposit in organic continuity, Goeppei't (7) in his 

 Monographic der fossilen Coniferen, devised a classification of coniferous wood in 

 which his composite genera united members of widely separated natural groups. 



Our wood belongs to his Cupressinoxylon type, which is characterized by 

 bordered pits on the radial walls of the tracheids in one row, or if in more than 

 one row then opposite ; resin canals wanting (or, if present, traumatic), and 

 abundant wood parenchyma, containing resin. 



Kraus, Kleeberg, Beust, Schroeter, Sanio, Schmalhausen, Conwentz, Knowlton, 

 Penhallow, and others pursued their investigations in the hope of finding constant 

 reliable diagnostic features for the different genera. In 1905 Gothan (8) showed 

 that the pitting of the medullary rays is a very important feature which cair be 

 effectively utilized for identification when due regard is paid to the other characters 

 of the wood. Gothan has founded the genus Taxodiorylon to include fossil 

 members of the Taxodineae previously placed in the composite fossil genus 

 Cupressinoxylon. Thus Taxodioxylon sequoianuni includes Sequoia-like forms ; 

 T. taxodianum, Taxodium-like species. 



Comparing our wood with the wood of living Conifers, we'find it cannot be : — 



Juniper or Libocednis decurrens— since the horizontal and tangential walls 

 of the medullary ray cells are unpitted (11) ; or one of the 



Cupressineae — since the pits on the radial walls of the tracheids are often 

 in more than two rows (16). 



We conclude it is one of the Taxodineae. 



Schroeter (18) foundin 1880 that the wood of Sequoia and Taxodium could be 

 distinguished by the fact that in Sequoia the horizontal walls of the resin cells 

 are of uniform thickness, and not pitted or nodulose as in Taxodiimi. Schroeter 

 evidently appreciated the diagnostic importance of this feature, as he mentions it 



