42 ROYAL SOCIETY OF CANADA. 



ra^^-eells. There is an important point of divergence, however, in the fact 

 that while in Libocedrus the pits on the lateral walls of the ray-cells 

 are simple, in Juniperus they are more or less conspicuously bordered, a 

 feature which tends strongly to give this latter genus a decided affinity 

 with Taxodivm and Sequoia. The separation of these genera from 

 Thuya and Cupressus thus i-ests upon well defined difierences in the 

 distribution of the resin-cells and the structure of the terminal walls of 

 the ray-cells. On the other hand, while Jjibocedrus approaches them 

 through the character of the pits on the lateral walls of the ray-cells, 

 by the same character Juniperus is separable fi-om both of these genera 

 and finds its affinity with Sequoia and Taxodium. A critical comparison 

 of the remaining generic characters will permit of more exact deductions 

 as to the precise relations in which these genera stand to one another. 



Libocedrus. 



Transverse. Summer wood thin, rather dense, usually showing a median 

 layer of more dense structure. 



Radial. The terminal walls of the ray-cells straight or somewhat curved, 

 entire, locally thickened or even coarsely pitted ; the pits on the 

 lateral walls of the ray-cells small and simple. Pits on the tan- 

 gential walls of the summer tracheids chiefly small and not veiy 

 numerous. 



Juniperus. 



Transverse. Summer wood thin but very dense. 



Radial. Terminal walls of the ray-cells thin and entire, more rarely 

 somewhat pitted ; the pits on the lateral walls of the ray-cells often 

 with a more or less obvious border. Pits on the tangential walls of 

 the summer tracheids chiefly small and not very numerous. 



Thuya. 

 Transverse. Summer wood thin, the structure rather dense. 

 Radial. The terminal walls of the ray-cells thin and not pitted or 

 locally thickened, usually much curved. Pits on the tangential 

 walls of the summer tracheids small to me<lium. ' 



Tangential. Ordinaiy rays narrow, the cells oblong, often very narrow, 

 more rarely oval . 



Cupressus. 



Transverse. Summer wood ver}^ thin, often barely distinguishable, the 



structure open throughout. 

 Radial. Terminal Avails of the raj'-cells commonly curved, thin and 



entire or often locally thickened. Pits on the tangential walls of the 



summer tracheids medium to large. 

 Tangential. Eaj'-cells chiefly broad, oval, or even transversely oval, the 



rays often more or less two-seriate. 



