the Anatomy of the Cone and Fertile Stem of Equisetum. 447 
them as such, and, as will be shown below, they form a definite system 
of strands, and constitute the scaffolding on which the whole vascular 
system of the cone is built up ’ (Barratt, p. 222). As a matter of fact 
the little groups of tracheides referred to in my description are undoubtedly 
protoxylem ; but some of the isolated tracheides clearly represent scattered 
metaxylem elements, slightly internal to the main bands of metaxylem 
These single cells are quite irregularly scattered, and do not usually persist 
for any distance ; not being disorganized, as are the tracheides of the 
protoxylem, they were presumably differentiated later than the latter. As 
my original description and a similar description of the corresponding 
tracheides in E. maximum (Browne ( 2 ), p, 234) not only failed to distin- 
guish between the slightly more internal cells of the metaxylem and the 
protoxylem, but also failed to recognize the continuity of the strands 
of protoxylem, they were not only inadequate, but misleading. Barratt’s 
conclusion that the system of proto- 
xylem strands represents the scaffold- 
ing on which the whole vascular system 
of the cone is built up will be discussed 
later. 
‘ As seen in transverse sections 
(Text-figs. 20 and 21) the metaxylem 
is separated from the protoxylem by 
parenchymatous cells . . .’ (Barratt, 
p. 223). This statement concerning 
the axis of the cone, taken from 
Barratt’s paper, is too sweeping a 
generalization. In E. maximum , it is 
true, the internodal protoxylem of the 
cone seems to be constantly separated 
from the metaxylem by parenchymatous cells. But in the bundle of 
E. palustre figured by Barratt in her Text-fig. 20 certain tracheides 
abut on the carinal canal, so that the protoxylem was presumably in 
contact with cells that develop as metaxylem. Metaxylem tracheides 
abutting on the carinal canals are also shown in figures of the internodes of 
the cone of E. palustre in my first paper on Equisetum (Browne ( 1 ), 
PI. LXV, Fig. 7). In the cone of E. limosum , so far as I have been able to 
observe, the protoxylem of the internodal strand is nearly always in contact 
with the metaxylem. This relationship is shown in Fig. 8 of PI. LXV of 
my first paper on Equisetum (Browne ( 1 )), and on a larger scale in Text- 
fig. 12 of the present paper, representing a transverse section of a small 
bundle in the internode of the cone of this species. As parenchymatous 
cells are interspersed in the metaxylem, one or two of the former may 
be situated between part of the metaxylem and protoxylem, but, as stated 
bundle from the axis of the cone of E. limosum , 
showing continuity of some of the metaxylem 
with the protoxylem. x c. 450. 
