44 ROYAL SOCIETY OF CANADA 



quite in accord witli the tendency at present prevalent among morpholo- 

 gists. 



It may also be pointed out in this connection that although char- 

 acters derived from the aspect of the transverse section are not of 

 leading importance, yet the}- may serve to confirm differentiations based 

 on other data. We thus find that in Thuya as a whole the tracheids are 

 distinguished by their large size, squarish forms and thin walls. In 

 Cupressus, on the other hand, they are usually more rounded, somewhat 

 smaller and generally thicker walled. These difïerences not only agree 

 with the limitations already assigned to Thuya and Cupressus, but they 

 show that the latter ai)])roaches the former through C. thyoides. It 

 would thus appear that, on anatomical grounds, there is a very close 

 relationship between Thuya and Cupressus, and that the limitations of the 

 two are not marked by strongly defined characters. This becomes more 

 apparent when it is recalled that Cupressus thyoides, on anatomical 

 grounds alone, could safely be referred to Thuya, when it would become 

 T. sphœroidalis, but when we consider the weight of evidence to be 

 derived from both the external and internal characters, it becomes clear 

 that this species belongs to Cupressus. 



From a paper published since these conclusions were reached, it is 

 interesting to note that Dr. Masters has arrived at the same results, but 

 from data derived wholly from a study of the external characters.^ 



With respect to the genus Cupressus as now constituted, it may be 

 ]jointed out that it is 8ej)arable into two distinct groups, the first of 

 which may be designated as Chamœcyparis, and the second as Cupressus 

 proper.''' The former includes C. thyoides, C. nootkatensis and C. Law- 

 soniana. The distinguishing feature is to be found in the character of 

 the pits on the tangential Avails of the summer tracheids, which are nar- 

 rowly lenticular and not very large. The second section embraces all the 

 remaining species which have heretofore been recognized under this 

 genus. The distinguishing feature is found in the conspicuously large 

 and broadly lenticular pits on the tangential walls of the summer 

 tracheids. 



Taxodium and Sequoia approach one another closely in the fact that 

 the pits on the lateral walls of the ray-cells are consijicuouslj^ bordered, 

 while the same element also serves as the basis of specific distinction. 

 Thus in Taxodium the pits are round and the orifice is narrowly oblong, 

 the border therefore broad ; while in Sequoia the pits are distinctly oval 

 or elliptical and the orifice broadly oblong, the border thus becoming 

 much narrower, and sometimes even obscure. These difierences are very 

 well defined and constant, and admit of no doubt as to the particular 



^ Journ. Lin. Soc, xxi., ;il2. 



2 Dr. Mastens's results again accord with my own in the subdivision of the genus 

 Cupressus, although, on anatomical grounds, 1 jjrcfer to reverse the order. 



