Internodal Vascular Strands of Equisetum. 19 
quite well. The same author figures too a bundle of the rhizome 
of E. silvaticum in which the lateral metaxylem is represented by a 
single element on each side (12, PI. IX, Fig. 9). According to 
Queva there is often only a single element of metaxylem on each 
side of the bundles of the rhizomes in E. maximum and E. limosum 
(14, pp. 29-30). 
In the only fossil rhizome of Equisetites the internal structure 
of which has been elucidated, that of E. noviodunense' the elements 
composing the lateral bands of metaxylem are exceptionally 
numerous (in the bundle figured 11-17 in each band) and each 
group of metaxylem extends from near the periphery of the bundle 
to the edge of the carinal canal (8, Text-Fig. 7 and PI. 9, Fig. 2). 
Text-Pig. 7 is copied from a schematic figure of such a bundle 
Text- Fig. 7. Transverse section of the vascular bundle of the rhizome 
of Equisetites noviodunense, after Fritel and Viguier. Magnification not given. 
given by Fritel and Viguier. As in the other Text-Figs, of the 
present paper the xylem is filled in in black. 
Reduction of the lateral groups of metaxylem is not confined 
to the rhizome. Milde figures a bundle of the aerial stem of 
E. trachyodon in which one of the lateral groups of metaxylem is 
developed in a typical manner and the other is totally absent (12, 
PI. XXXIII, Fig. 15). I have noticed that commonly in E. limosum 
lateral metaxylem is not present in the bundles for a part of the 
region lying between the last whorl of leaves and the annulus. 
Just below the level of insertion of the annulus, and on the 
breaking up of the nodal ring of wood, lateral metaxylem is present; 
but in the four cones of which I have made serial sections of this 
region it is absent from the bundles for a varying distance betwe en 
these two points. In the anatomically very different cone of 
E. cfictanleum I have also observed in some cases the absence and 
1 The tubers described as E. stellare were probably born on the rhizome 
of this species, 
