10. Tjie Comparative Anatomy and Phylogeny of the Coniferales. 

 Part 1. — The Genus Sequoia. 1 



By Edward C. Jeffrey. 



(Read April 15, 1003.) 



Introduction. 



In the present and following memoirs, it is my intention to describe certain features 

 of the anatomy of the Coniferales which appear to be of interest. The actual state of our 

 knowledge of the morphology and history of the group is not sufficient to justify much 

 certainty as to its classification, and consequently additions from any standpoint are likely 

 to be of value. The prevailing views as to the relationship of the various orders of the 

 Coniferales are based almost entirely on reproductive characters, and valuable as these 

 must always be, they constitute, nevertheless, but a single line of evidence. The study 

 of the anatomy of the older groups of Gymnosperms has done so much to clear up the 

 question of their affinities that it does not seem unreasonable to expect that a good deal 

 should be learned from investigations carried out on the same lines in the case of the 

 Coniferales, the prevailing Gymnosperms of the present day. It is to be anticipated that 

 the results of such investigations will serve to correct and supplement the conclusions 

 drawn from the study of the reproductive organs alone. 



The existing Sequoias are chosen as the subject of the first memoir, both because 

 of their interest as the sole survivors of a genus which once flourished in many species 

 throughout the entire northern hemisphere, and because investigations, already some- 

 what extensive although as yet incomplete, make it apparent that the genus Sequoia 

 presents a striking example of those rare and important forms which so infrequently per- 

 sist as links of transition between distinct and different natural orders of the present day. 



The Stem of Sequoia gigantea. 



Figure 1, plate 68, illustrates the structure of the wood in Sequoia gigantea as it 

 appears in a transverse section of the heart of an old stem. There are three annual rings 

 represented in the figure. In contrast to S. sempervirens, to be described later, the 



'Harvard Botanical Memoirs. — No. 7. 



