Embryo of Botrychium obliquum , Miihl. 1 5 1 
The cotyledon is provided with a very conspicuous basal sheath, which 
is not found in B. virginictnum . At an early period there is active growth 
at the base of the cotyledon, which soon extends over the stem apex and 
second leaf, which lie in a narrow, cleft formed by this overarching basal 
sheath of the cotyledon (Text-fig. 7, c). For some time the sheath is the 
most conspicuous part of the cotyledon, the apical portion of the leaf being 
relatively insignificant. 
The Root. 
The characteristic tetrahedral apical cell of the root becomes established 
at an early period, and soon shows a regular segmentation. The root grows 
rapidly and emerges on the ventral surface of the gametophyte (Fig. 4). 
It is much the most conspicuous feature of the young sporophyte and 
reaches considerable size before the emergence of the cotyledon. 
The root grows vertically downward through the tissues of the foot — 
or perhaps it would be more accurate to say it becomes incorporated with 
it, as the foot as such becomes quite unrecognizable, its tissues merging 
insensibly with those of the root, and its lower portion forms practically 
part of the root-cap, and it is ultimately destroyed as the root-cap is 
renewed from the segments of the apical cell. The axis of the root coincides 
with that of the cotyledon, so that almost from the first the bipolar character 
of the young sporophyte is established. 
Some time after the root has broken through the ventral surface of the 
gametophyte, the cotyledon elongates and ruptures the dorsal surface, so 
that the position of the young sporophyte is very much like that of the 
Marattiaceae, or Ophioglossum moluccanum (Fig. 6; Text-fig. 1). 
The apex of the cotyledon becomes differentiated into petiole and 
lamina, the latter being bent over, much as in B. virginianum. The young 
cotyledon shows a definite apical cell which appears narrowly triangular in 
longitudinal section. 
The massive basal sheath extends over the stem apex, which, together 
with the second and third leaves, is completely enclosed within the sheath 
(Text-figs. 8, 9). A single strand of procambium extends through the 
petiole, but no vascular tissue develops in this sheath. The bundle in the 
petiole is continued downward into the root without a break, and it is quite 
impossible to determine the limits between leaf and root. 
The second leaf develops in much the same way as the cotyledon, and 
its basal sheath envelops the stem apex and next younger leaf in exactly 
the same fashion. The details of the apical growth were not followed, but 
probably would not differ materially from the cotyledon. 
The leaf-trace of the second leaf begins to form almost as soon as the 
leaf can be recognized, the same being true of the third leaf. The bundle 
