282 THE AMERICAN NATURALIST.  [Vor. XXXIX. 
lycopods. From a study of the fossil Equisetales, especially 
Archaeocalamites, he concludes that these gaps are to be con- 
sidered as ramular gaps, although he admits that in Equisetum 
they occur opposite the leaves. He proposes the term “ clad- 
osiphonic" to designate a cylindrical stele, with ramular gaps, 
such as he assumes for the Equisetales and Lycopodiales. 
Admitting that the vascular system of Equisetum can be 
referred to a siphonostelic type, it is hard to see how we can 
reconcile Jeffrey's idea of cladosiphony with the facts. So far 
as we can see there is absolutely no difference in the arrange- 
ment of the bundles of the internodes and their intervening 
spaces in shoots which develop branches, and those which are 
without them. In all cases, the number of internodal strands 
— and, of course, that of the gaps between them — corresponds 
to the number of leaf traces developed from the foliar sheath. 
The gaps are equally present in the primary unbranched shoot, 
and in the densely branched sterile shoots of Equisetum arvense 
or Equisetum telmateia. It certainly seems hardly reasonable 
to suppose that an ideal branch — so to speak — could cause 
the development of a ramular gap, when no actual branch is 
present. 
. Jeffrey lays stress upon the fact that in Archaeocalamites, the 
branches are really opposite the spaces between the internodal 
vascular strands; but it appears! that Archzeocalamites was 
often very sparingly branched, but this does not seem to bear 
any relation to the presence of the alleged ramular gaps, which 
are perfectly developed whether branches are present or not. 
We see no reason why we should try to reduce the vascular 
system in the Equisetales to either of the types found in the 
other phyla of pteridophytes. The peculiar character of the 
stem, with its hollow jointed structure, would naturally involve 
quite a different arrangement of the tissues. Moreover, as has 
already been indicated, the origin of the vascular strands is 
entirely different from that of the typically axial vascular cylin- 
ders of the other classes. There is no valid reason why the 
separate strands in Equisetum may not have existed from the 
1 a 
Scott, Zoe. cit., p. 65: Potonie, Lehrbuch der Pflanzenpaleontologie, 1899. 
