4 
1go1 | ANATOMY OF THE OSMUNDACEAE 403 
Having described these for 0. regalis, Professor Bower aptly 
remarks :?5 
The meristem being thus at times irregular, and the subdivisions of the 
segments being variable, it is to be expected that the study of it (the apical 
region of the growing point) in longitudinal section would present difficulties, 
and I have not been able to trace any definite and characteristic mode of 
segmentation. Longitudinal sections cut from a considerable number of 
stems show that a conical apical cell is present. The relations of the sur- 
rounding tissues, and their reference to regularly succeeding segments are 
difficult to recognize. 
To these observations on the extreme apical end of the growing 
point we have nothing to add, but pass further down the stem. 
A short distance from the apex of .the stem, the various tis- 
sues, though in embryonic form, become apparent. The cylinder 
of wood, whose thin walled, unlignified cells are still provided 
with protoplasm and nucleus, can be distinguished from the pith, 
the parenchyma in the leaf gaps, and the immature phloem. 
The pericycle is rich in protoplasm, and its cells are radially 
arranged. At an earlier stage still, even before there is any evi- 
dent differentiation in the vascular tissues, the leaf traces can be 
Seen coming off from the cauline vascular axis. 
When the protoxylem can be first demonstrated by phloro- 
glucin and hydrochloric acid, the endodermis (both internal and 
€xternal in the case of O. cinnamomea) is also demonstrable by 
the same reagents, though not before. Zenetti has claimed” 
that at the time the protoxylem is formed, the endodermis, peri- 
cycle, “‘quergestreckte Zellen,”’ protophloem cells, and some 
Cortical cells are all in the same radial rows; and that, there- 
fore, all have originated from the same mother layer. Stras- 
burger has asserted?’ that the tissue lying in the stem between 
the phloem and the endodermis and occupying the position of a 
pericycle arises by tangential divisions with the endodermis out 
of the innermost cortical layer. Therefore, not the entire 
Phloeoterma, he claims, but the outer division product is that 
which gives origin to the endodermis. 
Bower: The comparative examination of the meristems of ferns as a phylo- 
§enetic study. Ann. Bot. 3: 323. 188 
*ZENETTI: of. cit. 64. 27 STRASBURGER : of. cit. 449. 
