16 
nature of the apical growth of the young organs of the embryo. 
An examination of a large number of preparations leads me to 
believe that in all of them there is at first a single stem initial, 
which in longitudinal section appears either triangular or trun- 
cate, but in cross section is nearly always four-sided. The seg- 
mentation of this cell does not appear to be very regular, but 
as a rule there are probably four series of lateral segments. 
As the latter are often nearly or quite as large as the primary 
cell, it may be that sometimes the lateral segments replace to 
some extent the primary initial cell, and that we cannot properly 
speak of a single stem initial except in the very earliest stages 
of the embryo. 
In the primary root there seems to be little question of the 
presence of the single initial cell, which may at first have a 
tetrahedral form, but is more likely to be truncate at the base, 
although it may have three series of lateral segments. A single 
initial cell was also seen in the later roots in both Kaulfussia 
and Angiopteris. 
The first indications of the vascular bundles become evident 
shortly after the establishment of the root apex. In the axis — 
of the cotyledon toward the inner side there is developed a 
strand of narrow cells, and this is continued downard until it 
joins a similar strand formed in the axis of the root. There is 
thus a single continuous strand of procambium cells traversing 
the young leaf and root. The stem seems to have no proper 
bundle of its own, and the primary stele — if such it can be 
called — belongs exclusively to the root and cotyledon. Except 
for the early development of the stem apex, which, however, 
is short and inconspicuous, the young sporophyte at the time 
_ the leaf and root emerge from the prothallium presents a marked 
similarity to the corresponding stage in Ophioglossum molucca- 
num. This resemblance is increased in Kaulfussia by the close 
similarity in the form and venation of the cotyledon to that 
of Ophioglossum. 
The vascular system of the adult sporophyte in the Marat- 
tiaceae is extremely complicated, especially in the large species a 
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