CONIFERALES 



339 



the relationship of Pinus to the other Coniferales. An excellent 

 illustration of the value of anatomical evidence in the case of 

 this problem is furnished by the interesting taxodineous genus 

 Sequoia. The Taxodineae as well as the nearly allied Cupres- 

 sineae are characterized anatomically by the organization of the 

 female cone and the structure of the wood. The scales of the 

 cone are superficially single, but in section they show the presence 

 of a double series of oppositely orientated fibrovascular bundles, 

 thus indicating the origin of the seed scales from the externally 



FIG. 246. Transverse section of the cone scale of Sequoia gigantea, showing a 

 double system of bundles with opposite orientation. 



double structures of the ovuliferous cone of the Abietineae 

 (Fig. 246). In the organization of their wood the Taxodineae differ 

 from the Abietineae in the absence of resin canals. There is, how- 

 ever, a resiniferous secretion produced by scattered parenchymatous 

 elements of the wood. In the structure of the radial parenchyma 

 a condition of simplicity contrasting with that found in the Abie- 

 tineae is manifested, for the marginal tracheids of the rays of the 

 Abietineae are conspicuously absent in the normal wood of the 

 Taxodineae in general and of Sequoia in particular. If we con- 

 sider the genus Sequoia in the light of the canons of anatomy 

 formulated above, very interesting results are reached. First, if a 

 transverse section of the axis of the cone or of the ovuliferous 

 scale of Sequoia gigantea be examined, resin canals reveal them- 

 selves in the wood in proximity to the primary xylem (Fig. 247). 



