599 
Cone of Equisetum maximum , Lam. 
true that separation of protoxylem and metaxylem, though less constant 
than in the cone of E. maximum , is characteristic also of the cone of 
E. arvense , in which the A anomaly has not been observed. But, apart 
from the inconspicuousness of the anomaly, which may have led to its being 
overlooked, the actual distance between metaxylem and protoxylem is 
markedly greater in E. maximum than in E. arvense , and is especially con¬ 
siderable in the lower part of the cone of the former species, in which region 
the A anomaly seems chiefly to occur. 
At the same time, though the depth of the axial protoxylem may have 
led to an increase in the number of cases in which the protoxylem of the 
sporangiophore fails to enter into connexion with that of the axis, it is clear 
that the xylem of the incoming trace shows, in E. maximum , a tendency 
towards reduction in the inner part of its course. For in the second or 
B anomaly the tracheides of the trace do not even enter the bundle. This 
very obviously represents a further stage in the reduction of the protoxylem 
of the trace within the axis of the cone. In this type of trace the phloem 
has not suffered any reduction. 
In the third or C type of anomaly—in the free trace—the reduction in 
the course of the trace in the axis is carried still farther. The phloem as 
well as the xylem ceases to be formed over a part of the course normally 
traversed by traces. In some cases the free strands of the sporangiophores 
approach very close to the stele ; in other cases they die out at the base of 
the sporangiophore without penetrating into the cortex. 
I have examined twenty examples of vascular strands belonging to 
sporangiophores which failed to reach the axial stele, five in Cone A and 
fourteen in Cone F of E. maximum , and one belonging to a cone of E. sylva- 
ticum . In two cases only, both in E. maximum , did the free bundle die 
out without entering the cortex. Of the eighteen other free strands some 
only died out when they had approached very close to the axial stele, and 
others died out almost as soon as they entered the cortex. A series could 
have been constructed showing traces dying out at every depth in the cortex. 
In E. maximum it is quite common for the individual tracheides of the free 
traces to become markedly wider (often about twice as wide) before they 
die out. Barratt has shown that in the cone of E. palustre the first tracheide 
of the trace to be differentiated abuts on the axial protoxylem and that the 
further differentiation of the tracheides proceeds outwards into the stalk of 
the sporangiophore (Barratt, p. 223 and Text-figure 19, p. 222). The 
enlargement of the tracheides before the dying out of the free trace suggests 
the possibility that, at least in the lowest whorl of the cone of E. maximum , 
the differentiation of the tracheides of the trace may begin in the distal part 
of the latter’s course and proceed inwards. On the other hand, any marked 
increase in the width of the tracheides as we pass inwards is not a feature of 
the normal traces. In this connexion it may be pointed out that should 
