Anatomy of the Cone and Fertile Stem of Equisetum. 249 
Number of 
the whorl. 
Average radius 
of the cortex . 
Diameter of stele. 
1 
o*6 mm. 
473 mm - 
4 
o*88 mm. 
4*53 mm - 
8 
0*92 mm. 
4 mm. 
12 
0*84 mm. 
2*6 mm. 
17 
0’72 mm. 
•46 mm. 
Branching Cone. 
Branching cones of E. maximum have been recorded by Stiles and 
Milde (Milde, p. 250), but not by Duval Jouve except as a great rarity, 
due to mutilation (Duval Jouve, p. 154). The abnormalities of Cone C, 
its branching and medullary strands, are confined to its upper part 
(cf. Text-fig. 4). At a distance of about 10 or 11 mm. from the apex of 
the cone (the latter had not fully elongated) it branches for the first time; 
a second branch is given off about a millimetre above the first, and a third 
one just above the second. The first and second branches are very much 
smaller than the parent cone, while the third is a little more than three- 
quarters of its size. 
As may be seen from the longitudinal reconstruction of the xylem of 
this part of Cone C, the vascular tissue of the lowest branch is of consider¬ 
able extent where it is inserted on the axis, and the elements that are 
passing out are cut very obliquely in transverse sections of the main cone. 
The xylem of the branch forms a nearly closed ring inserted very obliquely 
on three of the bundles of the axis, the two outer ones of the series con¬ 
tributing relatively few tracheides. The vascular tissues of the branch are 
given off by constriction of a loop of stelar tissue, so that no gap is left in 
the main stele. After the vascular tissue of one side of the branch has 
become free from the parent stele, but while the vascular elements of the 
other side are still in connexion with those of the parent axis, a trace goes 
off from the point of insertion of the vascular system of the branch on that 
of the main axis. This enters a sporangiophore situated at the junction of 
branch and cone. Soon afterwards the vascular tissue of the branch becomes 
finally free, constituting a slightly incomplete disto-proximally elongated 
ring that passes obliquely outwards. At the proximal end the ring of 
xylem is thicker, and from this region a trace is eventually nipped off in 
a direction pointing radially inwards ; but bending sharply round backwards 
it passes out, somewhat higher up, as a second trace, into the sporangio¬ 
phore already mentioned as inserted at the point of junction of the branch 
and main cones. A little higher up, while the stele of the branch is 
diverging very obliquely, a trace departs for another sporangiophore, one 
situated at the other point of junction of the branch with the main cone ; 
this sporangiophore, however, belongs definitely to the branch cone, and, 
like the sporangiophores of the latter, is somewhat smaller than those of 
the main cone at the same level. This branch cone pursues throughout its 
