1908] JEFFREY—FOLIAR GAPS 251 
statement made by the author, in his memoir on Equisetum, con- 
cerning the frequent failure to alternate at the nodes, which is char- 
acteristic of the strobilar strands of that genus. This feature is 
illustrated photographically in pl. 30, fig. 3, of the memoir. The 
author’s critics do not appear to have found this evidence sufficient. 
Itis important to insist on the correspondence of the micro-anatomical 
absence of leaf gaps in the cone of Equisetum with the non-alterna- 
tion of the axial strands of the cone at the nodes, because in some of 
the fossil forms we have only the latter evidence to go upon. It is 
perhaps a wise conservatism on the part of Dr. Scort to reject the 
evidence based on the frequent lack of alternation at the nodes, as seen 
in preparations of the bundle course in the cone of Equisetum. He 
can scarcely fail to be convinced by the microscopic demonstration 
of the absence of foliar gaps which has been given above and as 
represented in figs. z, 2, and 3. If it is reasonable to define a foliar 
8ap as a gap in the wall of the stele, or one of its component strands 
mM case the stele is not a continuous hollow cylinder, immediately 
above a leaf-trace, there are certainly no foliar gaps in the cone of 
Equisetum. The writer has satisfied himself that foliar gaps do 
Rot occur even when there is more or less complete alternation of 
the strands in the cone. £E. telemateia has been chosen for illustra- 
tion on account of the large size of the structures present. Similar 
tesults in every way are shown by E. arvense and E. hiemale. 
It is now possible to turn with advantage to the examination of the 
Outgoing foliar traces of the vegetative branches of Equisetum. As 
'S well known, the internodal bundles of one segment of the stem in 
Equisetum alternate with those of the next, in this respect presenting 
* contrast to the condition of the strands in the cone and in the more 
ancient extinct genera of the phylum. The internodal strands of 
Successive segments of the stem are joined in the region of the nodes 
by the so-called “nodal wood,” which consists of a dense mass 
of short reticulated tracheids forming ‘a completely closed ring. 
Fig. 5 shows a longitudinal section through an outgoing leaf- 
race and its corresponding cauline bundle. A large lacuna, the 
Protoxylem cavity, is seen on the right of the axial strand. This dis- 
‘ppears below the so-called “nodal wood.” The outward course of 
the foliar trace is steeply upward, in contrast to that of the sporophyll 
