iQig] DUPLER—TAXUS 359 



collateral endarch, in their terminal portions they contain not only 

 centripetal xylem, but are also accompanied by transfusion tis- 

 sue which may be both dorsal and lateral to the xylem elements 



(fig. 38). 



At the level of the uppermost scales the cylinder consists of 3 or 



4 large bundles (figs. 22, 48) which extend into the fertile portion of 

 the strobilus, where they branch, giving off finally a branch to each 

 sporophyll, the bundle extending a little way into the base of the 

 sporophyll stalk. In a young strobilus these bundles are repre- 

 sented only by elongated thin- walled elements, evidently pro- 

 cambium strands, which traverse the region between the base of the 

 sporophylls and the level of the upper scales (figs. 7, 8). These 

 strands remain in this embyronic condition until near maturity, 

 when they elongate and take on their vascular features in connection 

 with the growth of the "elongating region" of the strobilus axis. 

 In this "elongating region" the pith becomes larger in diameter 

 than in the lower portion of the strobilus, but shows no evidence of 

 being in any way a storage region; in fact, there would be little use 

 of a storage tissue at this stage in the development of the strobilus. 

 The several large bundles of the strobilus axis extend for some dis- 

 tance into the "elongating region" and then give off branches to the 

 various sporophylls, each of the large bundles supplying several 

 sporophylls in this way (figs. 13-22). Some of the branches may 

 unite and then separate (see the behavior of bundles // and e, and 

 also of I, c, and m, in figs. 18-22), although usually the bundles pass 

 rather directly to the base of the sporophyll (figs. 14-17, 44-47)- 

 Throughout the entire axis there is relatively a stronger develop- 

 ment of the phloem than of the xylem, the latter forming a narrower 

 zone than the former (fig. 48). Both xylem and phloem reach their 

 greatest development near the level of the upper scales (figs. 9, 22), 

 above this the xylem forming only a very narrow portion of the 

 bundle. Throughout the strobilus the xylem consists of spirally 

 thickened tracheids with bordered pits, the tracheids being rather 

 short, however, although in the elongated region of the axis they 

 are somewhat longer than at a lower level and the bordered pits are 

 fewer in number. The phloem of the portion above the scales 

 shows very little of the pitting present at a lower level, consisting 



