1922] BROWNE—EQUISETUM 461 
gave no written description of the course of the protoxylem above 
the departure of the xylem of the trace. In describing the nodal 
xylem of E. maximum, however, he states that at the inner edge 
of each of the masses of nodal wood some protoxylem elements 
(his trachées) are always found. These axial protoxylem elements 
are shown before the lignification of the nodal tracheids in his 
figs. 16 and 17, and after the differentiation of the nodal wood in 
his figs. 18 and 19 (all of E. maximum). Moreover, his fig. 22 
of E. litorale, in which two traces’ may be seen, already some way 
out in the cortex, shows very clearly the protoxylem persisting 
from the bundles of the internode below. In this figure the proto- 
xylem of each of these bundles has been divided into two groups 
of tracheids, and these sister groups have already diverged some- 
what from one another.? Eames (6) also regards the protoxylem 
as persistent, for in discussing the nodal, or as he calls it, the supra- 
nodal wood, he states: ‘‘Certainly its innermost elements are 
protoxylem, many radial sections show this condition clearly.” 
Later, in summarizing the nodal structure of Eguisetum, he states: 
“The carinal canal becomes discontinuous as it approaches the 
node. The protoxylem occupying that space enlarges, extending 
radially, then passes upward and forms the innermost tracheids 
of the supranodal wood.’ From these statements it would seem 
that Eames holds that the protoxylem persists through the node, 
although hardly as distinct strands; he seems rather to regard the 
inner elements of nodal xylem generally as protoxylem. 
The description of the nodal region of E. giganteum here given 
entirely confirms, so far as the course of the protoxylem is con- 
cerned, GWYNNE-VAUGHAN’s account. This might have been 
expected, as this author alone appears to have worked on the nodes 
of E. giganteum. It is, however, in agreement with Quéva’s less 
complete account of the protoxylem at the node, and in particular 
with his figures of E. maximum and E. litorale. 
6 Only a portion of the trace on the left is included in QuEva’s figure. 
7 on view of Quéva’s figures just mentioned, and of his allusion to the presence 
Of pr lem at the inner edge of the nodal wood, I cannot agree with Miss BARRATT’S 
Statement that he had noted that the xylem of each internode develops quite 
independently, only linking up subsequently by the development of the nodal 
tracheids. 
