1908-9. | THE STELE OF OSMUNDA CINNAMOMEA. 529 
that they afford a point of contact with the Gleicheniacee. With the 
latter we shall not deal in this connection. As to the former, a study 
of many stems of Osmunda cinnamomea, both young and mature, has 
led to the conclusion that the tissues composing these pockets are homo- 
logous with the tissues surrounded by the xylem, or to be more specific 
they are the lower and inner ends of the slanting medullary rays that 
have been closed in as the result of a centripetal proliferation of the xylem. 
The fact that an endodermis, apparently a portion or extension of the 
internal endodermis, is sometimes found in these pockets, and that often 
in the seedling and occasionally in the adult the pocket is not closed in 
on the axial side, but is a groove or bay, the lower extension of the medul- 
lary ray, lends colour to this view. Moreover, that there is a tendency 
for the cylinder of xylem to thicken in the direction of the pith is borne 
out by the behaviour of the seedling stele, by the circumstance that 
individual tracheids and even bundles are frequently found encroaching 
on the pith, and by the fact that sometimes the internal opening to a 
medullary ray is partially or wholly closed. If this view be correct, then 
the nodal pockets are to be regarded as strong proofs of an evolution 
” 
that tends towards ‘‘cladosiphony.’ 
PALAOBOTANY. 
It goes without saying that the strata hold the phylogenetic secret. 
Great interest has therefore attached to Penhallow’s account of Osmundites 
Skidegatensis, and Kidston and Gwynne-Vaughan’s description of a series 
of fossils regarded as Osmundaceous. Bower has hailed arguments based 
on this recently adduced stratigraphical evidence as the most cogent yet 
advanced in favour of the upgrade theory. ‘The readings from the strata 
are as follows (the quotations are from Bower’s lucid summary p. 539).— 
Grammatopteris from the Permian of Autun—‘‘with a solid homo- 
geneous protostele.”’ 
Chelepterts Zaleski from the Permian of Russia, ‘‘showing a proto- 
stelic state, but with the central region of the xylem differentiated from 
the peripheral.”’ 
Chelepterts gracilis from the upper Permian of Russia, and Osmundites 
Dunlop from the Jurassic of New Zealand, ‘‘with a continuous ring of 
xylem surrounding a central pith.” 
Osmundites Grbbeana from the Jurassic and Osmundites Chemnatzvensis 
from the Tertiary quartz of Hungary with ‘‘an interrupted xylem ring 
that surrounds pithonly,”’ and Osmundttes Skidegatensis from the Cretaceous 
which ‘‘shows internal phloem” and pith. 
