Cone and Fertile Stem of Equisetum. 253 
base of the cone and to the relatively large number of the strands here, and 
of members in the lowest whorl of sporangiophores. Where the stele is 
widest — in the middle or upper part of the cone — much more interfascicular 
xylem would be necessary to close an equal number of meshes. Here the 
internodal strands are far less numerous, and the diameter of the stele much 
greater, so that the internodal bundles are widely separated (cf. PL IX, 
Figs. 11 and 12). 
In Cones A and B of this species a single trace was given off at or near 
the level of the annulus. Unfortunately, its outward course could, not be 
followed, as just in this region the cortical tissues and those external to 
them had been injured by the hydrofluoric acid used to desilicify the cones. 
It was not even clear whether this trace ran to the base of a sporangium or 
not. In Cones C and D there was no sign of any such abnormality. It 
may be added that Milde especially states that the annulus at the base of 
the cone is quite normal in structure (Milde, p. 514), and that Duval-Jouve 
includes it among the species that do not show ‘ irregularities of the 
annulus’ (Duval-Jouve, p. 154). 
B. Description in E. gigantenm. 
In the internode of the fertile branch of E. gigantenm the central 
cavity is very large. In both my specimens, in the axis below Cone A and 
in branch E, the internodal bundles are eleven in number, each surrounded 
by a separate endodermis. The vallecular canals are conspicuous and the 
carinal ones show a tendency to be wider transversely than radially (PI. VIII, 
Figs. 3, 4, 7, and 9). The bundle in this region is approximately circular as 
seen in transverse section of the stem. The two lateral bands of metaxylem 
usually run straight outwards, nearly parallel to one another, and are inserted 
more or less at right angles to the middle group of xylem, usually chiefly 
represented by the carinal canal. The number of tracheides in the lateral 
bands seems to vary from five to twelve, but it is usually greater than in 
the internodal bundle of the stem figured by Milde, where there are only five 
tracheides (Milde, PI. XXI, Fig. 4). Not infrequently the bands of meta- 
xylem converge towards the periphery of the stele. As we approach the 
node the central cavity narrows, but there is no persistent diaphragm at 
this level. As the internodal bundles become laterally united into a ring 
the separate endodermes are replaced by a common inner and outer endo- 
dermis. The structure of the node is essentially that characteristic of the 
genus. Above the last vegetative node the central cavity widens some- 
what, though it does not attain to the same width as in the internode below. 
The separate bundles, each with an endodermis, are reconstituted and alter- 
nate with those of the previous internode. The carinal cavities reappear, 
but the vallecular canals are not re-formed. Milde asserts that the branches 
have six to eight, very rarely nine, ribs and bundles (Milde, p. 399). As 
