Internodal Vascular Strands of Equisetum. 15 
vascular bundles of the internodes 1 show a separation of the 
xylem into three distinct groups. In the internodes of the cones of all 
these species (Browne 2 and 3) the vascular tissues may be disposed 
in single separate bundles— i.e., in strands which at the node above 
give off the vascular supply of one sporangiosphore—or in bands 
giving off at the next node, traces to two or more sporangiosphores. 
As the vascular strands in the internodes of the vegetative axes 
are always single bundles it will be convenient in the subsequent 
discussion to select single internodal bundles of the cone rather 
than bands for comparison with other internodal, axial bundles. 
The structure of the bands is similar in essentials to that of the 
single bundles, but the former are, naturally, considerably wider 
than the latter. 
Text-Fig. 4. (a) Transverse section of small vascular bundle of upper 
part of fertile stem of E. giganteum , x circa 250. (b) Transverse section of 
small vascular bundle in one of the internodes of the cone of E. giganteum , 
X circa 325. 
Text-Pig. 5 a represents such a bundle, rather a small one, 
just below the lowest whorl of sporangiophores in E. arvense. 
Except that higher up the slight outward concavity of the xylem is 
replaced by a slight inverse curvature, so that the band of xylem 
conforms to the curve of the periphery of the stele, and that there 
is, in the example figured, a single large, possibly centripetal 
tracheid in the pith internal to the carinal canal, this bundle is 
1 The words internode and internodal bundles are here used, for con¬ 
venience sake, to denote the axis of the cone between the sporangiophores 
and the bundles at levels where the latter are not giving off traces. The use of 
the term is not intended to imply a true homology between a vegetative node 
and the axis of the cone at the insertion of the sporangiophores, since this 
depends upon the undecided and highly controversial question of the 
morphological nature of the latter. 
