352 BOTANICAL GAZETTE [may 
here both wings contribute to the formation of a single branch 
stele. Also procambium strands arise in the pith of the stem 
opposite the leaf trace (fig. 5, A,B); these develop a cambium 
directed toward the center of the stem, which produces a small 
amount of centripetal secondary wood which also contributes to the 
vascular supply of the branch. But the greater part of the vascular 
supply is furnished by the extra or accessory secondary xylem pro- 
duced by the renewed activity of the cambium (fig. 5,C). In this 
case, therefore, the branch connection consists of (1) accessory 
secondary xylem, (2) adaxial extensions of the centrifugal xylem of 
the leaf trace, and (3) a small mass of centripetal secondary xylem 
originating within the pith of the leaf gap. 
One of the other branches shows almost exactly the same con- 
nection, but the third branch shows a somewhat different situation. 
In it the vascular supply is composed principally of accessory 
secondary xylem; but a small mass of xylem appears in the peri- 
cycle of the stem and contributes to the supply of the branch. 
This pericyclic xylem is added to by a cambium directed toward 
the phloem; hence we may speak of primary and secondary peri- 
cyclic xylem, using the terms “primary” and “‘secondary”’ only to 
indicate the presence or absence of a definite cambium. The 
vascular supply of this branch, therefore, consists of (1) accessory 
secondary xylem and (2) primary and secondary pericyclic xylem. 
Botrychium obliquum.—F our branching rhizomes of this species 
were secured; three of these bore two branches each, and the other 
had three branches. In all but one of these, the apical region had 
been destroyed; but in this one case the rhizome had been injured 
at the side below the apical region, but without destroying the 
entire stele. In all the other cases, the branches developed near 
the apical region. The vascular connection of the lowest of the 
three branches mentioned above is shown by fig. 6. 
As shown by fig. 6, A, a very large development of accessory 
secondary xylem occurs entirely around the stele before the leaf 
trace separates; at the same level, a cambium has formed within 
the pith opposite the leaf trace and has developed a considerable 
mass of centripetal secondary xylem. The injury which occurred 
at the side of the stele at a slightly higher level has resulted in the 
