Anatomy of the Cone and Fertile Stem of Equisetum. 251 
existence a course remarkably oblique with reference to that of the main 
cone. Two more traces depart from the branch stele away from the parent 
cone; as it passes upwards and outwards the annular stele decreases con¬ 
siderably in size, and the xylem, closing on the side in which it was open, 
opens very slightly on the other side, to close again almost at once. After 
the departure of the two last-mentioned traces the stele condenses and 
becomes a large solid strand running into the apex of the branch cone and 
spreading out in the latter, which consists of a relatively large mass of tissue 
in which separate sporangiophores are not differentiated. 
It may be seen in the longitudinal reconstruction that on one side of 
the branch—in the direction in which the branch cone passes obliquely 
outwards—there are in the stele of the main cone two parenchymatous 
meshes not subtended by traces. The traces which we should expect to 
occur below these meshes are not developed, since, owing to exigencies of 
space, the sporangiophores they would naturally supply are not formed. 
The stele of the second branch of the cone is also given off from the 
parent cone without the formation of a gap, the parenchymatous mesh 
which may be seen above the end of the stelar branch clearly belonging, to 
judge from its size and position, to the trace found at the edge of the 
branch, but belonging to the main cone. The gradual formation of a loop 
of vascular tissue begins some time before it is finally given off by constric¬ 
tion as a branch stele, and three traces are given off from this loop before 
it becomes free, two on its distal side and one near one of its flanks. These 
pass upwards and supply the sporangiophores of the lowest whorl ; the 
latter are inserted on the side of the branch cone furthest from the parent 
cone; in this whorl there are no sporangiophores on the adaxial side of the 
branch cone, presumably owing to exigencies of space. Three parenchy¬ 
matous meshes appeared above this lowest incomplete whorl, two of them 
subtended by traces that have departed. The second and last distinct 
whorl of this branch of the cone was complete, but the stele had become 
narrower, and there were only four sporangiophores arranged more or less 
regularly round the axis. The traces for these sporangiophores depart 
from somewhat different levels, and pursue upward courses of varying 
steepness. Above this whorl the apex of the cone was undifferentiated 
into distinct sporangiophores. Unfortunately the sections of the extreme 
apex were lost in mounting, but a sufficient number were preserved to show 
that in all probability it followed the type normal for this species. 
The third case of branching is somewhat different. It is apparently 
an example of unequal dichotomy, resulting from the gradual constriction 
of the stele near, but not quite at the middle. The slightly larger stele 
remains terminal in position, and at the level of separation of the two steles 
consists of seven bundles in an internodal condition. The smaller, or 
branch stele, diverges at a much more acute angle than did the steles of 
