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AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
joins the foot. As the root grows, it pushes downward through the foot, 
which is practically eliminated and is no longer recognizable. The young 
sporophyte is thus bipolar in structure, and the stele, as we have seen, is 
continuous through the cotyledon and root. 
It is not until the cotyledon and primary root are fully developed that 
the bud which is to develop into the definitive sporophyte first becomes 
evident. This begins as a group of meristematic cells close to the stele of 
the root — exactly in the way a secondary root arises. The first two leaves 
of this bud are formed quite independently of the apical meristem of the 
young bud. The stele of the first leaf of the bud joins directly with the 
stele of the primary root, while that of the second leaf is joined to the base 
of the stele of the first root developed from the bud (fig. 2). 
It is thus clear that the fibro-vascular system in the sporophyte of 
0. Moluccanum begins as a single continuous strand extending from the 
petiole of the cotyledon into the primary root and practically of the same 
structure throughout, the xylem and phloem of the "collateral" foliar 
portion being continuous with the corresponding tissues of the "monarch" 
root portion. This primary "stele" is not a "protostele," i.e., it is not 
"concentric" in structure, and, moreover, it is not a cauline structure. 
A study of the older sporophyte shows that much the same condition 
prevails as in the earlier stages. The leaf-traces unite with root bundles 
and with the older leaf-traces, and there is thus built up the open "dictyo- 
stele" found in the adult rhizome. There is no indication of the develop- 
ment of any stelar tissues except those belonging either to the leaves or 
to the roots. 
BOTRYCHIUM 
In Botrychium Virginianiim the structure of the axial stele is quite 
different from that in Ophioglossum. At an early stage, the axis of the 
young sporophyte shows an almost unbroken cylindrical stele enclosing a 
central pith instead of the large-meshed " dictyostele " of Ophioglossum. 
In the very young sporophyte a single strand of procambium extends through 
the axis of the cotyledon into the primary root ; but as these organs usually 
make a marked angle with each other, the primary vascular strand is 
strongly bent instead of being straight, as it is in Ophioglossum Moluccanum. 
Very soon the second leaf is developed, and a similar vascular strand is 
formed in it, which unites with the primary vascular bundle near the point 
of junction between the petiole of the cotyledon and the base of the primary 
root (fig. 3), and the fusion of the three bundles appears as a closed ring in 
cross section. 
The traces from the later leaves behave in much the same way, and the 
massive "siphonostele " found in the older stem is thus built up. 
For details see "The Eusporangiatae," pp. 89-93. 
^2 Jeffrey, E. C. The gametophyte of Botrychium Virginianum. Trans. Canad. Inst. 
5: 1-32, 1898. 
