1 88 BIOLOGICAL LECTURES. 



narrow, more rarely oval, while the terminal walls of the ray- 

 cells are conspicuously devoid of pits, or local thickenings. In 

 Cupressus, on the other hand, the rays are distinctly broader, 

 the cells are oval, round, or even transversely oval, rarely 

 oblong. The walls are also much thicker, as a rule. The 

 terminal walls of the ray cells are thin and often entire, but 

 they also frequently show very obvious local thickenings. 

 These characters are well defined and, so far as a large amount 

 of material will permit a definite conclusion, constant. These 

 characters, therefore, may safely be taken as marking the limi- 

 tations of the genera. On these grounds, Chamaecyparis nut- 

 kaensis of Spach must be restored to the genus Cupressus under 

 Lambert's name of C. nootkatensis. The genus Chamaecyparis 

 thus disappears altogether, a change which is quite in accord 

 with the tendency at present prevalent among morphol- 



ogists. 



It may also be pointed out in this connection that, although 

 characters derived from the aspect of the transverse section are 

 not of leading importance, yet they may serve to confirm differ- 

 entiations 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 differences not only agree with 

 the limitations already assigned to Thuya and Cupressus, but 

 they show that the latter approaches the former through 

 C. nootkatensis and C. Lawsoniana. 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 any strongly defined characters. This 

 becomes more apparent when it is recalled that Cupressus 

 thyoides, on anatomical grounds alone, could safely be referred 

 to Thuya sphaeroidalis, but when we consider the weight of 

 evidence to be derived from the external characters, together 

 with those derived from the internal structure, 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 



