454 EDWARD C. JEFFREY ON 



branches, or even of vigorous leaf traces. In 8. sempervirens, resin ducts appear only as 

 tangential rows in isolated annual rings, probably in all cases in response to injury to the 

 tissues of the wood. 



The occurrence of resin canals in the reproductive axis of 8. gigantea is in all proba- 

 bility to be regarded as an ancestral feature. It is significant in this connection that 

 certain species of Abies, which have no resin ducts in the wood of their vegetative organs, 

 retain them in the ligneous cylinder of their cones, e. g., A. grandis, A. nobilis, etc., etc. 

 In the case of these species the presence of resin ducts as a general feature of structure 

 of the wood in the order to which they belong, justifies the conclusion that the occurrence 

 of resin canals in the wood of the female reproductive axis is an ancestral character, which 

 has disappeared in the wood of the vegetative stem. A parallel case is presented by 

 the peculiar mesarch bundles found by Dr. Scott in the peduncle of the cones in certain 

 Cycads (The anatomical characters presented by the peduncle of Cycadaceae, Ann. bot., 

 1897, vol. 11). Bundles of this nature were present in the medullary crown of the vege- 

 tative axis of certain of the primitive fossil Gymnosperms and of the Cycadofilices. In 

 the living Cycads, mesarch bundles have disappeared iu the vegetative stem, but are some- 

 times retained in the reproductive axis and quite generally in the vegetative and repro- 

 ductive leaves. In *S'. gigantea, resin ducts retained in the wood of parts of the female 

 cones, likewise occasionally occur in the leaf traces as well, thus presenting a striking 

 parallel to the mesarch bundles of the Cycads, in the manner of their distribution. The 

 presence of resin canals under certain quite definite conditions in the first annual ring of 

 the branches of 8. gigantea, supplies a further argument for regarding the occurrence of 

 resin ducts in the wood of this species as the retention of an ancestral feature, for it is 

 only natural to find such a character reappearing in the first zone of woody growth of 

 the young branch. This conclusion is also confirmed by the presence of a similar feature 

 in the young branches of certain Abietineous species to be subsequently described. 



The phenomena of injury furnish additional evidence in favor of the view that the 

 ancestral stock from which the Sequoias have been derived, was characterized by the 

 presence of ligneous resin ducts, for it appears justifiable to regard the formation of 

 tangential rows of traumatic resin canals in the injured wood of both living species of 

 Sequoia as a reversion to an ancestral condition, especially in view of the phenomena 

 described in the last paragraph. This explanation of the phenomena resulting from 

 injuries to the woody tissues in the species under discussion is confirmed by the fact 

 that similar traumatic resin ducts are commonly formed as the result of injury to the 

 wood in the Abietineae, in contrast to the Cupressineae, etc. 



The hypothesis that the Sequoias have come from ancestors characterized by the 

 presence of resin ducts in their woody tissues, receives a further support from the con- 



