Foliar Gaps in the Osmundaceae. 1 
BY 
EDMUND W. SINNOTT, 
Austin Teaching Fellow in Botany, Harvard University . 
With Plates XI and XII. 
I N 1900 Jeffrey (1) proposed the division of all vascular plants into two 
great phyla : the Lycopsida , comprising the Lycopodiales and Equise- 
tales, and characterized by ventral sporangia, small leaves, and the absence 
of foliar gaps in the central cylinder; and the Pteropsida , including the 
Filicales, Gymnosperms, and Angiosperms, all of which have dorsal 
sporangia, large leaves (at least primitively), and foliar gaps. That these 
two phyla differ in the position of their sporangia and in the size of their 
leaves, as far back as we have geological record, is now generally agreed, 
That they are clearly divided in the manner of departure of the leaf-trace 
is not, however, universally admitted. The question as to whether there 
are foliar gaps in the Lycopsida has been thoroughly discussed by Jeffrey 
in a recent paper ( 2 ). In the other main group, the Pteropsida, gaps are 
unquestionably present in all the families save one, the Osmundaceae. 
That there are numerous cases of the absence of foliar gaps, both in the 
fossil and the living members of this group, has recently been strongly 
urged by several writers, notably Kidston and Gwynne-Vaughan ( 3 ). The 
present investigation was undertaken to clear up the relation of leaf-trace 
to central cylinder in this interesting family. 
More or less complete material of seven members of the group was 
obtained. These are the three common American species of Osmunda , 
O. regalis, L., O. cinnamomea , L., and O. Claytoniana , L.; Todea barbara , 
Moore ; and the three filmy Todeas, T. saperba , Colenso, r.hymenophylloides , 
Rich, and T. Frazeri , Hook, and Grev. Only portions of the mature 
leaves could be secured in the last species. 
The central cylinder of the stem in the Osmundaceae consists, as is 
well known, of a ring of xylem strands, separated by parenchymatous ‘ rays ’, 
and surrounding a pith. Outside the xylem is a more or less continuous 
ring of phloem. The method of departure of the leaf-trace from the 
cylinder has been worked out by several investigators, among the foremost 
of whom is Zenetti ( 4 ). The first indication of the formation of a foliar 
1 Contributions from the Phanerogamic Laboratories of Harvard University, No. 20. 
[Annals of Botany, Vol. XXIV. No. XCILI. January, 1910.] 
