26 i 
Cone and Fertile Stem of Equisetum . 
than in other species in which the anatomy of the cone is known ; (b) by 
the not infrequent development of wide internodal tracts of xylem involving 
the absence of parenchymatous meshes over median traces ; (c) by the fact 
that closure of parenchymatous meshes more often involves the formation 
of additional tracheides than the oblique course and ultimate fusion of 
groups of tracheides lying on either side of the mesh ; and (d) by the fact 
that this fusion of strands, owing to the formation of additional tracheides, 
not infrequently occurs considerably below the node. 
5. Both in E. hyemale and in E. gigctnteum the sporangiophores of 
successive whorls alternate with considerable regularity. But the traces at 
their insertion on the axial stele do not alternate regularly with those of the 
whorls above and below. In both species regular superposition occurs 
when parenchymatous meshes persist unnarrowed on either side of a trace- 
bearing strand through two or more nodes. This superposition, being due 
to poor development of axial xylem at the nodes, is less common than in 
E. maximum or in E. limosum. Within the species the specimens with less 
well-developed xylem show more numerous examples of superposition of 
traces. 
6. The traces of the sporangiophores of E. giganteum are the most 
massive yet described for the genus. 
7. The traces of the lowest whorls of the cone of E. hyemale tend, even 
when young, to be deflected slightly downwards while passing outwards 
through the cortex. 
8. In E. hyemale the axis is narrower at the base than in the middle or 
slightly above the middle of the cone ; but the internodal axial strands 
and members in a whorl are markedly more numerous at the base of the 
cone. Consequently the vascular bundles are much closer to one another 
in the annular region than in the wider parts of the axis of the cone. This 
probably partly accounts for the relatively high number of meshes closed at 
or near the level of insertion of the annulus. Above the latter numerous 
fresh meshes arise. 
9. In E. giganteum the annulus is normally sporangiferous, the 
sporangia being attached by their upper ends to the free incurved edge of 
the annulus. A vascular strand runs to the point of insertion of each 
sporangium. The number of the latter bears no constant relation to that 
of the strands in the axis or the lobes of the annulus. The annular bundles 
may remain free from or be connected with the axial stele ; they may branch 
or remain unbranched. 
10. E. giganteum differs from the other species studied in that no fresh 
parenchymatous meshes arise above the annulus. The nodal nature of the 
axis at the level of the insertion of the latter is, however, supported by the 
analogy with other species and by the closure of some parenchymatous 
meshes in this region. 
