ANATOMY AXD PIIYLOGENY <^F THE CONIFERALES. 449 



and from the root as well, except in the axial primary wood as just mentioned above. 

 In all eases where 1 have been able to make the experiment, however, I have succeeded 

 in l)ringiug abont the formation of resin canals as a result of injury, in the wood of 

 species of Abies which are normally without them, even in their reproductive axis. It 

 is interesting in this connection to note that certain fungous diseases causing iniury to 

 the wood of species of Abies produce the same result. It seems necessary to record the 

 traumatic reactions of the woody tissues of the genus Abies because, as I shall attempt to 

 show at the end of this essay, they supply an interpretation of the similar phenomena 

 in the case of Sequoia. 



The Leaf of S. (jirjoiited. 



In figure 23, plate 70, is seen part of a section tlirough the base of the leaf of »S'. 

 giganfea. In the center of the figure lies the leaf trace fianked by the two lateral win^-s 

 of transfusion tissue, which are so characteristic of the lower part of the foliar bundle 

 in Sequoia and its allies. Above and below the leaf trace are masses of collenchyma- 

 toid tissue. The feature of greatest interest in the figure is, that contrary to other 

 described coniferous leaf traces, the foliar bundles of S. gir/ai)fea contain a resin duct. 

 The duct is (|uite of the normal type and is surrounded by a single, almost complete row 

 of resiniparous cells. In some cases, however, as is often found in tJie resin canals of the 

 Sequoias, the parenchymatous lining of the canal is far from being contiiuious, and the 

 tracheids as a result often abut directly on its lumen. It must not be supposed that resin 

 ducts occur in all the leaf traces of S-. gigantea, for this is not the case. They appear 

 only to be present in the bundles of the very lai'ge leaves of exceptionally vigorous 

 branches of mature trees (i. e., trees which have already ripened seed) . All the material 

 which I have, showing this feature, came horn the Gray herbarium of Harvard univer- 

 sity; but in spite of the necessarily bad condition of preservation consequent on its 

 origin, there seems to be no reasonable doubt as to the nature of the canals, which I have 

 described a))ove as resin ducts. Tlie longitudinal range of the resin ducts of the foliar 

 bundles of the largest leaves in mature trees of Sequoia gigantea is quite limited ; for 

 they appear only after the leaf trace has passed quite out into the cortex of the branch, 

 and indeed after it has traversed a cousideralile part of its upward and outward course. 

 There is as a consequence no communication between the resin ducts of the first annual 

 ring of wood in the branches and those appearing in the leaf traces. Like the other 

 modes of occiu-rence of resin canals described above, there is an entire absence of correla- 

 tion with other similar tissues. The resin ducts of the leaves disappear again very shortly 



