330 BOTANICAL GAZETTE [NOVEMBER 
of the Coniferales. Attention has been called in the descriptive part 
of this article to the striking points of structural resemblance presented 
by S. Penhallowii to certain abietineous species. The medullary 
rays, for example, although they lack the marginal tracheidal cells _ 
characteristic of the typical Abietineae, have distinctly differentiated 
marginal cells which find a close parallel in the medullary rays of the 
genus Abies. Further, the marginal cells of the medullary rays of 
our species are crystallogenous, as are those of Abies. Another 
feature of strong resemblance to the Abies and the Abietineae is the 
marked pitting of the terminal walls of the medullary ray cells. Thi 
character is absent or poorly marked in the cupressineous series. 
Equally strong indications of abietineous affinities are to be found 
in the structure of the wood. The resin cells, which are such a marked 
feature of cupressineous woods, are almost absent in our species. The 
few which are present are confined to the outer surface of the summer 
wood, as in the abietineous genera Tsuga and Abies. The strongest 
argument, however, for the transitional nature of our fossil is that 
presented by the ligneous resin ducts. As has been pointed = ad 
the foregoing paragraphs, resin canals occur in both the horizontal 
and vertical planes in the wood of S. Penhallowii as the result of 
injury. In this feature it presents a striking resemblance to the 
normal state of affairs in the abietineous genera Pinus, Picea, Pseudot- 
suga, and Larix. In another place® I have pointed out that 
normal occurrence of vertical resin canals in the wood of the sm 
cone scales, peduncle, and jirst year’s growth of strong branches ° 
sexually mature trees of S. gigantea is good evidence that pes 
had come from ancestry characterized by the presence bo 
resin canals. In both S. gigantea and S. sempervirens resin a 
of the vertical type only occur in the secondary wood as the pei ats 
injury. In view of the conditions found normally in S- se trau- 
the matter of the occurrence of resin canals, I have argued me of S- 
matic resin canals are a case of reversion in the injured ¢ of the 
gigantea and S. sempervirens. Here we have an ees a by 
value of experimental morphological evidence when han out that 
that of comparative anatomy. Further it may be of Natur 
8 Jerrrey, E. C., The genus Sequoia. Memoirs of the Boston Society C 
History 5: no. ro. 
