58 Slopes. — The Missing Link in Osmundites . 
within each point of the seven-horned central mass. It is much to be hoped 
that further specimens of this interesting species may come to light and 
yield longitudinal sections to settle this and other points about the stele 
structure. 
When one mentally subtracts the seven bays of secondary tissue, the 
star-like form of the primary wood becomes very evident, as is seen clearly 
in Photo 3. This is so remarkably like the central axial tissue of some of 
the palaeozoic Botryopterideae that one feels that Kidston and Gwynne- 
Vaughan’s statement that they believe the Osmundaceous and the Botryo- 
pteridean series to have had a common ancestor (Part IV, p. 468) has, 
in this new plant, a strong piece of confirmatory evidence. They say : ‘ An 
Osmundaceous stele with a continuous ring of xylem and a mixed pith 
corresponding exactly to that of Zygopteris Grayi has not yet been found ; 
if it did exist, the difference between it and the stele of Zygopteris Grayi 
would lie mainly in the star-like outline of the latter.’ The present species 
has a star-like outline much like the latter. But it appears to be more 
primitive in having apparently a solid xylem and not a mixed pith. The 
presence of secondary tissue is, of course, a very unusual feature in the 
ferns of any age, and may, particularly when the primary wood is small, be 
considered a primitive feature. 
The secondary wood forms seven compact bays which, together with 
the somewhat stellate primary wood, complete the roughly spherical shape 
of the stele (see Photo 3). The secondary and primary tracheides are not 
sharply distinguished, and, where they are adjacent, it is hard to say which 
is which. In the outward direction, however, they appear in [fairly definite 
radial series, with a maximum of about seven tracheides in each radius. 
The greatest diameter of these secondary tracheides is somewhat less 
(1-5-2 ju) than the central primary elements of the wood, which vary between 
2 /x and 3 /x. 
The pitting of these tracheides also, so far as can be judged from hints 
revealed in the transverse sections, seems to be that usual in the Osmunda- 
ceae. The phloem and outer tissues are not preserved, and the space they 
must have occupied is filled with crystallized matrix. Surrounding the 
stele, and evidently outside the phloem, is a layer of large strongly-marked 
cells. These cells appear very comparable with those described as endo- 
dermis in Osmundites Carnieri (see Kidston and Gwynne-Vaughan, 1914, 
PI. XLIV, Figs. 37 and 40). Outside this layer is again another space of 
crystallized matrix, in which must have lain the small, recently detached 
meristeles. At a short distance, about 2-5-3 mm - ( see Photos 4 and 5), the 
surrounding leaf bases are preserved ; those nearer the axis are considerably 
crushed and distorted, probably owing to their delicacy. Those lying 
rather farther from the axis are less distorted, and some of the larger ones 
seem but little crushed (see Photo 1 and Photo 6). 
