466 BOTANICAL GAZETTE [JUNE 
of course do not occur below the node of E. giganteum, since, as 
GWYNNE-VAUGHAN himself has shown, the internodal metaxylem, 
as well as the nodal xylem of this species, consists of reticulately 
thickened elements. Fig. 7 shows diagrammatically the distribu- 
tion of the xylem at the nodes and internodes of E. giganteum. 
The spirally thickened protoxylem is there shown by broken vertical 
lines, while the reticulately thickened tracheids, nodal wood, and 
internodal lateral strands alike are shown by a dotted surface. 
For the sake of convenience the internodes have been drawn as 
much shorter than they would be in a mature specimen. 
In E. hiemale the lateral strands are smaller than in E. giganteum, 
but it seemed clear from serial sections that they too completely 
lose their identity in the nodal wood. Indeed, this occurs relatively 
quickly, for the crossbar of the tracheids, which as we approach 
the node forms a bridge between the two lateral strands (fig. 1, 
stage 3 of E. giganteum), is-here usually two, three, or more cells 
in depth, and therefore nearly as deep as the lateral strands. ‘Thus 
the latter hardly project at all outward, and are early merged in an 
almost straight, oblong band of metaxylem lying outside and 
parallel to the radially narrow carinal canal. GWyNNE-VAUGHAN 
also claimed that in E. maximum no metaxylem departed from the 
axis to the leaf trace, although he made no statement on this point 
for E. gigantewm. Eames, however, claims that the metaxylem 
unquestionably takes part in the formation of the leaf trace, and 
figures such a case for E. hiemale, in which species the metaxylem 
is well developed. In nodes from three stems of E. hiemale exam- 
ined the departing protoxylem carried with it metaxylem tracheids 
from the periphery of the bundle. At least in my specimens, 
however, these were less numerous than in E. giganteum, and 
died out before the trace with its endodermis was completely free 
from the axial bundle. In serial sections of nodes from two fertile 
stems of E. maximum and from a fertile stem of E. sylvaticum 
examined the metaxylem did not, in most of the bundles, con- 
tribute to the formation of the leaf trace, although occasionally 
in E. maximum and not infrequently in E. sylvaticum two or three 
reticulate tracheids, at the level of the departure of the trace, did 
bend out into the cortex, where, however, they seemed to die out. 
