Anatomy of the Cone and Fertile Stem of Equisetum. 683 
were therefore indistinct ; to ascertain the structure of more mature apices 
the upper parts of Cones B, D, and E were cut. In all three the last node 
gave off six traces, but in Cones D and E two of these seem to have entered 
one sporangiophore. In Cones B and E two unequal bands of xylem, much 
wider than the ordinary traces, entered the terminal sporangiophore, while 
in Cone D a similar wide band of xylem and two smaller strands enter the 
terminal sporangiophore ; before entering the sporangiophore these two 
smaller strands approach very close to one another, but diverge again with- 
out fusing. These two small strands certainly seem to correspond to one 
of the bands that enter the terminal sporangiophore of Cones B and E. 
In the cone of E. palustre , of the variety polystachion as well as of 
more typical specimens, the proportion of xylem at the apex seems to be 
relatively great. Here, indeed, it commonly forms a ring extending up- 
wards from a point below the uppermost whorl of sporangiophores. In 
Cone A such a ring is only formed a little way above the last whorl, and as 
the stele has already narrowed considerably, the ring is very narrow ; but 
even here the amount of xylem relatively to the diameter of the stele is 
above the average amount in other parts of the cone. In all three apices of 
cones of E. palustre examined the ring narrows rapidly as we pass upwards, 
and ere long its condensation gives rise to a small solid circular strand 
(i. e. it no longer encloses any parenchymatous cells) ; in the variety poly- 
stachion this narrowing of the ring and its condensation into a circular strand 
are effected partly by the fact that certain tracheides pursue an inward, 
centripetal course. This small circular strand is the trace of the terminal 
sporangiophore. 
In E. limosum the trace of the terminal sporangiophore is formed as 
the continuation of one of the xylem- strands of the internode below. In 
Cone B the others seem to die out, while in Cone A they give off, after the 
departure of the traces, contributions to the strand of xylem that persists ; 
the latter then narrows very rapidly, becomes circular and concentric, and 
passes upwards into the terminal sporangiophore as its trace. 
As regards the structure of the sporangiophores, Eames has shown that 
their traces are concentric and mesarch, and I have nothing to add to his 
remarks (Eames). 
The Structure of the Vegetative Nodes. 
Before considering the region transitional from fertile stem to cone 
a few facts as to the structure of the vegetative nodes must be reviewed. As 
is well known the bundles in an internode of the stem of Equisetum consist 
of three groups of xylem. Of these the carinal or protoxylem group is 
situated medianly and at the edge of the pith ; its annular or spiral vessels 
early become disorganized, giving rise to the carinal canal, upon the edge of 
which abut a few tracheides that have not been torn. The two other groups 
