[PENHALLow] NOTES ON TERTIARY PLANTS 59 



and that they are therefore contemporaneous species, and any con- 

 clusions as to their relative sequence in development must rest entirely 

 upon structural variations, which indicate that T. distichum is the more 

 recent, as already shown. 



CUPRESSOXYLON MACKOCAKPOIDES, n. Sp. 



Cretacous, near ]\Tedicine Hat, Assiniboia, N.W.T. 



Transverse.— Growth rings rather broad. Tracheids of the spring wood round 

 but thin-walled through the obvious effects of decay; rather uniform 

 in regular rows, and passing gradually into the rather thin but con- 

 spicuous summer wood. Resin passages Avholly wanting. Resin 

 cells not recognizable. Medullary rays prominent, often 2 cells wide, 

 distant 1-6 rows of tracheids. 



Radial.— Mi'unUiiry rays wholly devoid of tracheids. Kay cells more or less 

 conspicuously contracted at the ends, equal to about six spring 

 tracheids; the upper and lower walls rather thin and sparingly 

 pitted; the terminal walls chiefly straight, sometimes curved, not 

 pitted or obviously thickened locally; the lateral walls with oval or 

 round pits, 1-2, chiefly 2 per tracheid. Bordered pits in one row, 

 chiefly distant, round. Fits on the tangential walls of the summer 

 wood not recognizable. Resin cells present on the outer face of the 

 summer wood (?), 30« wide and 125 u long. 



Tangential. — Fusiform rays wholly wanting. Ordinary rays numerous, low to 

 high, often more or less 2-seriate, rarely 3-seriate in part; the cells 

 variable, chiefly broad, oval or round or sometimes transversely oval. 

 Resin cells rather numerous, usually very long, the resin scattering in 

 small globules. 



Of the two specimens representing this species, one has no assigned, 

 locality, but it is presumably from the same deposit as the other, with 

 which it is structurally identical, and which was obtained from 

 Twemty-mile Creek, near Medicine Hat. The structure has been so 

 altered by decay and subsequent compression, that details respecting 

 some of the most essential characters cannot be determined with cer- 

 tainty. There is nevertheless no reasonable ground for doubting the 

 identity of the specimens with Cupressus, and among existing species 

 they are most nearly related to C. macrocarpa. Indeed, the agreement 

 is so close in nearly all respects that there is little reason for doubting 

 that C. macrocarpoides is the ancestral form of the existing species, buL 

 m the absence of sufficient data to establish the identity beyond all 

 question., I prefer to designate it by the name selected. 



