Anatomy of the Cone and Fertile Stem of Equisetum 685 
in accordance with modern ideas as to the conservatism of reproductive 
axes. Queva has figured and described a curved band of xylem in the 
vegetative bundles of the upper end of the internode of E. littorale (Queva, 
p. 33, Fig. 31). The xylem of the internode of the cone, where the latter 
contains a circle of more or less equidistant strands, often forms curved 
bands with the concavity facing outwards, though the curvature is less than 
we should have to assume for the vegetative node if the lateral strands are 
supposed to mark the ends of such a band. When wide tracts of xylem 
involving more than one strand of the internode below persist through an 
internode of the cone, the curvature of the band of xylem is slightly in the 
inverse direction, so that the xylem forms segments of a circle concentric 
with the outline of the stele. Traced downwards the terminal tracheides of 
the curved xylem-strands of the cone are continuous with the tracheides of 
the lateral metaxylem of the internode below the cone. We may add here 
that according to Leclerc du Sablon the xylem in the bundles of the tubers 
of Equisetum is not broken up into a carinal and two lateral groups, but 
vessels and parenchyma are mixed irregularly (Leclerc du Sablon). 1 
Milde has figured a similar bundle of a tuber (Milde, PL I, Fig. 33). In 
the tubers of the fossil Equisetaceae recently described by PTitel and 
Viguier, the xylem of each bundle appears to consist of an oval mass of 
parenchyma mixed with tracheides. Queva has shown that the elements 
of the nodal wood are lignified after those of the carinal group, but before 
the lateral metaxylem of the internode. In 1901 Gwynne- Vaughan, from 
a study of E. gianteum and E. hiemale , concluded that the lateral strands 
may be traced through the node and across the upper surface of the ring of 
nodal xylem ; that after passing above and across the latter they fuse wfith 
the similar adjacent strand of a neighbouring bundle to form the alternating 
strands of the internode above (Gwynne-Vaughan). Queva, however, 
writing six years later, seems to be unaware of Gwynne-Vaughan’s remarks ; 
he states that the nodal reticulate tracheides are c in direct relation to the 
metaxylem, the elements of which show above the node transitional mark- 
ings ’ (Queva, pp. 18-19). According to this botanist, therefore, the 
tracheides of the lateral strands are gradually replaced by reticulate nodal 
elements as we pass upwards ; higher up this xylem dies out, except at the 
points where the wood persists as the lateral metaxylem-strands of the 
internode above, and at these points the reticulate thickening of the elements 
is gradually replaced by spiral. Ludwigs in a recent paper seems to be of 
this opinion, though he expresses himself somewhat differently, saying that 
metaxylem-elements are initiated on both sides of the bundle, and are 
especially numerous at the level of the nodal diaphragms ; that after the 
departure of the protoxylem into the leaf the two groups of metaxylem 
1 This author also states that throughout the tuber the bundles form an irregular network, a point 
which would repay further investigation. 
