1908] JEFFREY—FOLIAR GAPS 257 
ficial examination of the anatomy of this genus might lead to the con- 
clusion that the perforations in the tubular stele, which are sometimes 
lateral to the outgoing leaf-traces, are to be regarded as true foliar 
lacunae. 
3. Foliar gaps are likewise absent in Tmesipteris, and recent 
statements as to their presence are based on misinterpretation or 
misconception. Perforations in the stele are here also found some- 
times lateral to one or more leaf-traces, but these cannot be regarded 
as true foliar gaps. 
4. Foliar gaps are absent in the Lepidodendreae and the Sigil- 
lariae, but in the more modern species of the latter perforations of 
the tubular central cylinder are sometimes found, which have the 
same relations and are susceptible of the same explanation as are the 
similar perforations in Phylloglossum and Tmesipteris. 
5. Foliar gaps are unquestionably absent in the cone axis of 
Equisetum, and on the basis of comparative anatomy are absent also 
in the vegetative stem. Similar statements apply to the reproductive 
and vegetative axes of Calamites. Archeocalamites has no foliar 
8aps in its vegetative stem. 
6. The Lycopsida as defined by the author are clearly marked off 
from other plants by a palingenetically microphyllous habit, the 
absence of foliar gaps in the tubular stele, and by the possession of 
or with adaxial sporangia. They constitute a great natural 
Phylum, 
In conclusion the writer wishes to express his thanks to Miss 
SYKEs, Professor A. A. Lawson, Professor G. J. Prerce, Dr. Hot- 
MAN (Stanford University), and Mr. L. A. Boopze for material 
which they have kindly put at his disposal. 
HARVARD UNIvERsItry 
EXPLANATION OF PLATES 
PLATE XVII 
Fic. 1.—Transyverse section of part of the cone of Equisetum telemateia. X 15. 
Fic, 2.—Transverse section showing the axial bundle and its outgoing foliar 
trace of the cone of EF. telemateia. X25. 
'G. 3.—Longitudinal section of the same. X25. i 
Oe eee section through the supranodal wood of the vegetative 
