149 
Embryo of Botrychium ob lignum , MiihL 
more advanced ones were found, the true nature of these apical (?) cells must 
for the present remain in doubt. 
The next stages, which were a good deal more advanced, were re- 
markably like corresponding ones in the Marattiaceae, especially Danaea . 
Text-fig. 6 , A-D, shows four of a series cut vertically, showing plainly 
the basal wall (b-b). The embryo was broadly oval in outline, the major 
axis being transverse, as it is in corresponding stages of various Marattiaceae. 
Occupying the central portion of the epibasal region, there is a group of 
superficial columnar cells, which may mark the beginning of the cotyledon, 
but this is not at all certain. In this embryo there was nothing which 
could be interpreted as a root, and the whole of the hypobasal portion 
formed the large foot. 
The next stage found (Text-fig. 6 , e) was considerably older, and also 
strongly resembled the embryo of Danaea . The vertical axis of the 
embryo was now equal to the transverse, and the upper part was slightly 
pointed with what looked like a single apical cell marking the position of 
the cotyledon. The primary vascular bundle, which later extends through 
the cotyledon and root, is indicated by a group of actively dividing cells 
below the cotyledon apex. 
The primary root in B. obliquum closely resembles in its origin that of 
Ophioglossnm and the Marattiaceae. A single initial cell arises near the 
centre of the embryo, very near the basal wall (Text-fig. 6, e). In the 
embryo figured, the first segment has been cut off from the initial cell. It 
is difficult to say whether the root belongs to the epibasal or hypobasal 
region, as it is so near the centre of the embryo. 
Text-fig. 7, A, shows two longitudinal sections of a more advanced stage 
in which the apical cell of the root is very conspicuous and the primary 
vascular bundle extends from the cotyledon into the root. The section 
passes through the apex of the cotyledon, which shows a very evident apical 
cell. The apical cell of the root is extremely conspicuous and closely 
resembles that of the roots of other Ophioglossaceae. 
As in Ophioglossum moluccanum and the Marattiaceae, there is no 
question that the vascular system in B. obliqnum begins as a single strand 
common to cotyledon and root and having no connexion with the stem 
apex. The latter (Text-fig. 7, A, 11) at this stage consists of a small group 
of superficial cells, lying somewhat to one side of the centre of the 
flattened area forming the top of the embryo, which is somewhat top- 
shaped in outline, closely resembling similar stages in Danaea } There 
is a single apical cell, which is somewhat larger than the neighbouring 
cells. In longitudinal section this cell is oblong in outline, with a broad, 
truncate base. In older stages, the lateral walls of the apical cell 
usually converge towards the top, which is thus narrower than the base. 
Campbell: Eusporangiatae, Figs. 1 17-19. 
