526 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Voy. VIIL- 
by a simple process of expansion. ‘The pith was thus regarded as stelar, 
in which respect the family stood as an exception among the Filicinez. 
Seward and Ford (12), Tansley (13), Kidston and Gwynne-Vaughan (7), 
and Bower (2) have recently adopted the same view, and have stretched 
it to cover the dictyostele of Osmundites Skidegatensis, the siphonostele 
of Osmunda cinnamomea with its internal endodermis and locally distribu- 
ted internal phloem (4, 6), and the siphonostele of Todea hymenophylloides 
with its more or less distinctly marked internal endodermis (12). 
They believe that the more complex steles of these forms have been 
derived from a medullated stele such as that of Osmunda regalis by a differ- 
entiation of the pith, and hence.that the occurrences of internal endodermis 
and internal phloem are indications of an upward evolutionary tendency 
towards the amphiphloic siphonostele—an attainment most nearly 
realized so far in Penhallow’s Osmundites Skidegatensts. 
An opposite view, in harmony with Jeffrey’s stelar theory, was elab- 
orated prior to this by Faull. It was contended that the history of the 
stele of the Osmundacee has not been exceptional as suggested by Van 
Tieghem, and, therefore, the stage following the protostelic was the am- 
phiphloic siphonostelic, which was brought about by an “‘intrusion”’ of 
the phloem, endodermis, and cortex into the protostele. It was further 
maintained that the simpler steles of living forms represent various degrees 
of modification from the amphiphloic siphonostele. Accordingly the 
siphonostele of Osmundites Skidegatensis is believei to be the most primitive 
known in the Osmundacee, and that of Osmunda regalis one of the most 
specialized. 
In attempting to work out the phylogeny of this family, investi- 
gators have pursued three lines of inquiry, namely ontogeny, comparative 
anatomy, and paleobotany. ‘There are indications that a fourth, experi- 
mental morphology, is important, but it has not yet been exploited. 
ONTOGENY. 
Kidston and Gwynne-Vaughan (p. 774) sum up the contentions of 
the anatomists who hold that the Osmundacee represent an ascending 
series in the following words: ‘‘The theory of reduction has met with 
strong opposition from subsequent writers, Boodle, Seward and Ford, and 
Chandler, who base their objection chiefly upon the confirmatory evidence 
in the stem of the young plant. We entirely agree with their criticisms, 
and prefer to regard the Osmundaceous type of vascular system as derived 
directly from a primitive stele possessing a true pith, surrounded by a 
stout and perfectly continuous ring of xylem. The leaf-traces departed 
