40 ROYAL SOCIETY OF CANADA 



americana the outer trucbekls of the summer wood sometimes develop 

 very distinct spirals ; also in some of the hard pines — notably P. taeda — 

 there is a decided tendency in the same direction. But in none of these 

 •cases is the development carried so far as to involve confusion with 

 respect to the law already stated. On the basis of these considerations 

 it becomes obvious that, on anatomical grounds, there is good reason for 

 regarding the Taxaceœ and Coniferœ as distinct families, a conclusion 

 which serves to materially strengthen similar deductions already derived 

 from general morphological considerations.' 



The Taxaceœ embraces only two genera within the limits of North 

 America north of the Mexican boundar3\ These are Taxus and Torreya, 

 and between them the principal difterential feature is to be found in the 

 shape and size of the ray-cells, as exposed in tangential section, and thus, 

 to some extent also, the width of the ray. Thus in Taxus the cells are 

 oblong and usually very narrow, and investigation contirms the belief 

 that there is no essential deviation from this rule, since the most marked 

 alteration of form occurs in those rays which become more or less two- 

 seriate, when the cells are sometimes rather shorter and broader, and thus 

 assume a more or less oval form. (Plate I., fig. 3.) In Torreya^ on the 

 other hand, the ray-cells are always much broader and larger and distinctly 

 oval, more rarely oblong. (Plate I., tig. 5.) Supplementary difïeren- 

 tiations also appear in the compactness of the tracheid spirals and in the 

 general character of the transverse section. If the compact spirals of 

 Taxus canadensis (Plate I., fig. 2) are compared with the somewhat dis- 

 tant spirals of Torreya calif ornica, the distinction between these two 

 genera is at once apparent. Similar differences exist, in a more or less 

 pronounced degree, between other species of these genera, and they be- 

 come very obvious in a comparison of Taxus canadensis with Torreya 

 tax/folia. (Plate I., fig. 4.) A third and much less reliable, although 

 valuable supplementary character, is to be met with in the general aspect 

 of the wood as exposed in transverse section. In the genus Taxus thS 

 tracheids are chiefly small, thick-walled, variable in size, and with more 

 or less conspicuously rounded lumens — the structure, as a whole, being 

 rather compact. These characteristics apply with particular force to T. 

 canadensis and T. brevifolia, but are less applicable to T. flo7'idana, iiincp, 

 the structure in this species shows a distinct approach to the chai'acter- 

 istics of the genus Torreya. 



In Torreya the tracheids are relative!}^ large, the walls rather thin, 

 the lumens are, as a rule, more distinctly squarish, while the structure, 

 as a whole, is distinguishable by its rather open texture. While such 

 differences may very correctly be associated with generic distinctions, it 

 must be recalled that the aspect of structure in transverse section varies 



' Geol. Surv. of California, Botany, ii., 109 ; Jour. Lin. Soc, xxx., 1. 



