1922] BROWNE—EQUISETUM 455 
bundle (figs. 3 and 4, stages 11, 12). This deepens rather rapidly, 
and another shallower parenchymatous depression appears oppo- 
site it on the inner edge of the metaxylem, between the two groups 
of protoxylem (fig. 4, stages 12, 13). In this inner indentation a 
carinal canal now forms, or, in other words, the protoxylem strands 
arising from different bundles of the internode below approach 
one another, and, partly by an increase in their number, become 
united into a single group (fig. 4, stage 14). By this time the 
metaxylem has decreased considerably in amount, and forms a 
deeply lobed mass, the two lobes being separated by the deepening 
parenchymatous sinus in 
st 
the outer edge of the er at Bas es. 
xylem. The lobes become t crl f 3a 
5 
‘ 
‘ . 
\ 
less and less massive, and i \ 
' 
are soon only connected \ ee 
2a 1 
by a narrow crossbar. ““—"e?> ane \Q 
When this breaks, as it OE eee 
does a little higher up, 
the structure of the bun- 
dle (fig. 5, stages 15, 16) vividly recalls stages 1 and 2 of fig. 1, 
although the metaxylem is as yet more extensive than in these. 
By a decrease in the number of tracheids, however, the bundles 
soon assume the internodal appearance shown in fig. 1, stage 1. 
As in the cone-bearing stem of E. limosum described by the 
writer (3), so at this node of E. gigantewm an inverted cone of 
‘relatively thick-walled cells, staining deeply with Bismarck brown, 
hangs down from the upper limit of the node for a little distance 
into the internode. 
Fic. 5.—Stages 15 and 16; X about 120 
Ill. Nodes of smaller fertile branches 
The upper nodes of the cone-bearing branches of E. giganteum, — 
although resembling in essentials the node of the main stem previ- 
ously described, were on a much smaller scale, and showed one or 
two points of difference. The branches at my disposal all pos- 
sessed eleven ribs and bundles, and their steles were but little 
over a millimeter in diameter. There is no definite diaphragm, 
neither is there an inverted cone of persistent tissue hanging down 
