670 Browne. — Contributions to our Knowledge of the 
increase of xylem at the node, the mesh separating them is little or not at 
all constricted in this region. 
Of none of the other cones were the series of sections sufficiently 
extensive in a vertical direction to afford useful data as to the height of the 
meshes ; Cone E, however, seemed to have about the same relative amount 
of xylem as Cone C, and Cone F relatively rather less. The proportion of 
xylem in Cone G seemed to be about the same as that in Cones A and B. 
The series of sections of the other cones were too short to allow of such 
generalizations. 
The nature of the meshes originating below the lowest whorl of 
sporangiophores will be considered in discussing the region transitional from 
cone to fertile stem. 
Even a superficial glance at a reconstruction of the xylem of a cone 
of E. arvense in which the wood is relatively well developed, as it is in 
Cone A, gives the impression of nodal bands or a nodal ring of xylem, 
broken up in the internodes by meshes of parenchyma and usually broken 
too at the nodes by the persistence of one or two of these meshes. The 
cone of E.palustre does not give this impression. Here, too, parenchyma- 
tous meshes originate above the sporangiophore traces, but many of them 
persist upwards through more than one internode. Thus Cone A of this 
species, which had the largest proportion of xylem, had 19 meshes of the 
first, 9 of the second, 2 of the third, 4 of the fourth, and 1 of the fifth 
order ; Cone B of the same species had 6 of the first, 7 of the second, 1 of 
the third, 1 of the fourth, 3 of the fifth, and 1 of the seventh order. Cone D 
of the reduced variety polystachion had only four whorls ; it had one mesh 
of the first, one of the second, and one of the third order. Besides these, 
other meshes originating below the sporangiophores, and therefore below 
the cone proper, persist through one or more internodes of the cone ; they 
are relatively more developed in Cones B and D, which have less xylem than 
in Cone A. Their nature will be considered in connexion with the tran- 
sitional region. The series of sections of Cone C of E. palustre was too 
short to afford data as to the height of the parenchymatous meshes. 
In E. arvense the sporangiophore traces are never, except at the 
extremely reduced apical region of the cone, given off from the edge 
of a strand or band of xylem, though when a relatively wide parenchyma- 
tous mesh persists through a node, the traces of the strands abutting on it 
may depart from a point very near to the edge of the xylem. In E. palustre, 
however, correlated with the less vigorous development of the axial xylem, 
traces not infrequently arise from the edge of the strand ; i. e. at their point 
of origin they abut on a mesh persisting through the internode, while many 
other traces depart from a point very near the edge of a xylem-strand 
(cf. Text-figs. 3 and 4). These kinds of traces may conveniently be referred 
to as lateral or slightly internal. Traces that depart from what is more or 
