1908-9. ] THE STELE OF OSMUNDA CINNAMOMEA. 527 
from this stele in a protostelic manner, that is without leaving any de- 
pression or gap into which the external tissues could subside. Bower 
(p. 538) likewise affirms ‘‘that a good basis for an opinion opposed to a 
theory of reduction is to be found in the ontogeny of the living plants, 
for in the seedlings there is at first a protostele without internal complica- 
tions, which expands later, and becomes medullated; but at first the pass- 
ing out of a leaf-trace does not necessarily interrupt the continuity of the 
xylem ring; leaf-gaps are not found till later.” 
Professor Bower’s contention is met in full, and Kidston and Gwynne- 
Vaughan’s in part at least by the ontogeny of Osmunda cinnamomea. 
Incidental to the departure of the leaf-traces there are flattenings and in- 
dentations of the xylem, parenchyma pockets, gaps, and a pith formed by 
the closing of agap. ‘The internal endodermis even originates as an eccen- 
trically situated pocket at the inner entrance to a medullary ray, just 
where a leaf-trace is being given off, and it continually tends to connect 
With the external endodermis through the leaf-gaps. Internal phloem 
and wide-open leaf-gaps through which cortex and pith communicate 
were not found, however, in my material. Their absence may be indi- 
cative of reduction expressed in the seedling stage. The fluctuations in 
the course of development and the consequently long-drawn-out juvenile 
stage are matters of interest, the explanation of which is much to be 
desired. 
COMPARATIVE ANATOMY. 
(a) The homologies of the pith. 
At the conclusion of his studies on the seedlings of Leptosporangiate 
Ferns, Chandler expressed the opinion that the pith of Osmunda cinna- 
momea Was of extrastelar homologies and in accordance With this view 
fairly accurately forecast the description of the seedling as given in this 
paper. The features of the adult stem that favour this view are (1) the 
textural continuity through branch-gaps of like tissues, namely, external 
endodermis with internal endodermis, parenchymatous cortex with paren- 
chymatous pith, and sclerenchymatous cortex with sclerenchymatous pith, 
(2) the same phenomenon in connection with the leaj-gaps of Osmundites 
Skidegatensts, (3) the occasional continuity of external endodermis and 
internal endodermis, cortex and pith through the leaf-gaps of Osmunda 
cinnamomea, (4) isolated tracheids in the pith are surrounded by a ring 
of endodermal cells. These are essentially the same criteria as those 
applied to ferns whose piths are admittedly extrastelar. 
Granted that the pith of Osmunda cinnamomea is extrastelar, the 
similarity of the stelar anatomy throughout this family raturally leads 
