June, 1921] 
CAMPBELL THE EUSPORANGIATE FERNS 
The vascular strands of the first two leaves are collateral in structure, 
and after their fusion near the junction of the cotyledon and primary root, 
the xylems of the two bundles are easily recognizable and are continuous 
with the two xylems of the diarch root (fig. 7) . 
Fig. 7. Five cross sections of a series from a young sporophyte of Danaea Jamaicensis. 
A shows the two primary leaf-traces; B and C, the fusion of these to form the solid stele of 
the young plant; D, the transition region of the sporophyte; E, the stele of the root. 
It is clear that the central region of the young sporophyte is not strictly 
a cauline structure, since the cotyledon and primary root are in no sense 
appendages of the stem, which at this stage consists only of the very small 
area in the immediate vicinity of the apical meristem. Moreover, the foot 
contributes a considerable amount of the outer tissue in the central region 
of the young sporophyte. 
As the new leaves are formed, close to the stem apex, their steles unite 
with those of the older ones, and there is thus built up a "dictyostele," 
much like that in Ophioglossum. After about seven leaves have been 
