1901] ANATOMY OF THE OSMUNDACEAE 415 
degeneration except the entire disappearance of internal endo- 
dermis is. observable in suitable specimens. 
When we attempt to orient the other species amongst them- 
selves, the task is more difficult, and of little importance. As 
already indicated, a closer study of development may afford 
more precise proofs. In the mature stems we have seen that 
O. regalis occasionally has sclerenchyma in the medulla, that 
there are ramular gaps, though usually small, and that the external 
endodermis is well developed. In OQ. Claytoniana, on the other 
hand, sclerenchyma is never found in the medulla, ramular gaps 
are infrequent, and the external endodermis shows indications of 
degeneration. In neither of these species is internal endodermis 
or internal phloem present. The probability, therefore, is that 
in the genus Osmunda there is a series, O. cinmamomea possessing 
the most primitive type of central cylinder and O. Claytoniana 
the most degenerate, O. vegalis occupying a middle position, but 
nearer to the latter. It is merely interesting to note in passing 
that Professor Campbell concluded from his study of the pro- 
thallia of O. Claytoniana and O. cinnamomea, that the gametophyte 
of the former was more specialized in many particulars, in other 
words, was less primitive in type than the latter. 
fifth, does a study of the vascular system help to determine 
the phylogenetic position of the Osmundaceae ? 
It was stated at the beginning of this paper that botanists 
have regarded the: Osmundaceae as possessing an anomalous 
form of central cylinder among the Filicales, their reason being 
that it seemed to present more of the features of a central 
cylinder such as is typical for dicotyledons, that is, a medullated 
Monostele in Van Tieghem’s terminology. In determining the 
Position of the family, therefore, in any natural system of 
Classification, it was hopeless to try to reconcile this single 
dicotyledonous character with the remaining filicinean characters, 
and so the vascular system in the family was regarded as 
anomalous. 
CAMPBELL: On the prothallium and embryo of 0. Claytoniana and O. cinna- 
™omea. Ann. Bot. 6: 49. 1892. 
