11 2 Sinnott.—Foliar Gaps in the Osmundaceae . 
Seward and Ford ( 5 ) observed conditions in a young plant of T. hymeno- 
phylloides . They remark that in its essential features it agrees with 
O. regalis , as described by Leclerc du Sablon. After the appearance 
of the young pith, however, these authors observed that the first leaf-traces 
did not necessarily cause a break in the xylem ring, though well-marked 
gaps were formed by all the subsequent traces. The figure which they 
present of such a gapless condition resembles very much the early stage in 
one of those cases of delayed gaps to which we have above called attention. 
Another section, through the very base, or youngest part, of a mature stem, 
shows a ring of xylem broken at one point by the departure of a leaf-trace, 
thus presenting a state of affairs identical with that found in the species of 
Osmunda. These observations of Seward and Ford have been rather widely 
cited by other authors as evidence that the primitive method of departure 
of the leaf-trace in the Osmundaceae is a gapless one. Careful serial 
sections should be made through the region in question, however, before 
we may feel sure of the actual state of affairs. 
Chandler (10) studied young plants of T. hymenophylloides and 
T. Frazeri. He simply states that his results in the former species con¬ 
firm those of Seward and Ford, but gives no detailed account of the 
anatomy of the stem. In T. Frazeri he investigated only the very young 
stem, before the appearance of the pith. The single leaf-trace whose 
departure he observed was simply constricted off from the protostele. 
He examined the ‘ seedlings ’ of a large number of species of ferns and 
found that in every case, where the young stele is tubular, the departure of 
a leaf-trace causes a break in the continuity of the xylem ring. 
The writer was able to examine the stems of young plants of 
O. regalis and of O . cinnamomea. They were too old, however, to show 
the continuous ring of xylem described by Leclerc du Sablon and Faull. 
Wherever the trace leaves the cylinder, in either of the two species 
observed, a wide gap results (Fig. 9). 
The slender bases of mature stems of T. hymenophylloides and of 
T. superba were also examined, and in every case pronounced, though 
narrow, gaps were observed. Fig. 10 shows this young condition in the 
former species. Several gaps are visible, as well as two leaf-traces in 
different stages. 
As far as the evidence from the young plant goes, therefore, it seems 
clearly to sustain the view that leaf-gaps are primitive structures in the 
Osmundaceae. Kidston and Gwynne-Vaughan, however, have used the 
structure of the ‘ seedling ’ to support the theory that the original con¬ 
dition in the family is a gapless ring of xylem. They cite the observations 
of Seward and Ford on T. hymenophylloides , which, as we have seen, would 
be much more reliable had they been made from a study of careful serial 
sections ; those of Chandler on T. Frazeri, which could have nothing to do 
