594 FILICALES 
As seen from Figs. 330 8B, C, the sporangial mother-cells are deeply 
sunk, and the first segment-walls may insert themselves upon the basal 
wall, as is shown in sporangium (3), Fig. c; in other cases the segment 
walls may cut the lateral walls of the mother-cell (e.g. sporangium 4). 
But, however this may be, the first segmentations are those characteristic 
of bulky sporangia. 
The sporangia themselves are of large size, and vary somewhat in 
form, being in D. Cuécta of an almost pear-like shape with very oblique 
ring, while in D. AMenziesit the ring is more longitudinal. The stalks 
are relatively thick though elongated, and show in transverse section a 
rosette of six or seven cells (Fig. 330, central drawing). As the published 
drawings of Dicksonia sporangia are not altogether satisfactory, I have 
represented those of D. Menzéesi’, Hook and Baker, from four different 
points of view. Fig. 330 H shows how, on the peripheral face, the con- 
tinuous ring of the annulus surrounds the relatively large thin-walled area ; 
the indurated part of the annulus is shaded, and of the rest, four smaller 
cells (connective cells) are seen on either side of the group of five cells 
which form the stomium. The central face is shown in Fig. 330 F; 
but in this case the stomium is composed of only four cells, while five 
connective cells are seen on either side of it. Fig. 330 E shows a lateral 
view of the side on which the annulus is completely indurated, and Fig. 
330 G shows the stomium as again a group of five cells, while two pairs 
of “connective” cells are seen on either side of it. From these drawings 
the form and large size of the sporangium, and the position of the annulus 
are clearly seen, while we also conclude from them that the number of 
cells of the stomium and connective is not constant. 
The orientation of the sporangia has been examined in D. Schiedei, 
Chamissot and Mensztesit; at the margin of the flattened receptacle it is 
not uniform, but the sp$rangia seated on the sides nearer its base show 
in the majority of cases, though with no strict uniformity, an orientation 
on the Gleicheniaceous plan. 
Notwithstanding the large size of the sporangia, the output of spores 
in Dicksonia is not a high one. Enumerations were made for D. Menziesit 
with 62, 63 as the result, and in D. antarctica, 64. Clearly 64 is the typical 
number for these Ferns. 
ANATOMY. 
The vascular system of Dzcksonta can only be properly understood 
in the light of the simpler forms, and especially of the Dennstaedtiinae. 
Nevertheless it will be described here, and referred to again later. It 
has been examined in D. Barometz and Culcita by Gwynne-Vaughan,} 
who finds the system of the axis to consist of a cylindrical dictyostele 
surrounding a large central pith. The meshes of the dictyostele are the 
foliar gaps, and from the lower limit of each arises a leaf-trace in the 
1 Ann. of Bot., xvii., 1903, p. 708. 
