252 BOTANICAL GAZETTE [ocToBER 
trace. Its tracheids obviously take their origin in the region of the 
protoxylem lacuna and below the “nodal wood.” If the usual 
definition of a node be accepted, as marked by the outgoing leaf- 
traces, the so-called “nodal wood’? of Equisetum in reality is above 
the node. Fig. 4 shows a transverse section through a part of the 
“nodal wood” intervening between the bases of two branches. The 
leaf-trace lies just outside the mass of reticulated tracheids which 
compose the wood of the “node.” It is obvious that there is no break 
in the mass of tracheids corresponding to the leaf-trace. Above the 
incorrectly designated “nodal wood” are the internodal bundles of 
the next segment of the stem, and between these are parenchymatous 
gaps, which on account of the alternation of the internodal bundles 
in different segments are above the leaf-traces, since the latter take 
their origin from the bundles of the lower internode. Professor 
CAMPBELL and Dr. Scorr regard these as foliar gaps. They lack, 
however, one important feature of foliar gaps, for they do not occut 
immediately above the traces, as should be the case with true foliar 
gaps. All other foliar gaps with which we are acquainted show 
this feature. The onus of proving that the internodal lacunae of 
Equisetum are really foliar gaps appears consequently to lie upon the 
investigators who claim that they are to be regarded as such. It will 
be clear from the anatomical facts described above that in view im 
the relation of the leaf-traces to the so-called “nodal wood” it is quite 
incorrect to designate the ring of tracheids which lies above the out- 
going leaf-traces as “nodal wood.” It can only be called accurately 
supranodal wood. This distinction is a very important one to make, 
moreover, on phylogenetic grounds. » 
As a sequel to the description of the actual anatomical relations 
of the outgoing leaf-traces of the vegetative stem of Equisetum, . 
is natural to proceed to the discussion of the evolutionary OF phy 
genetic significance of the observed facts. The following citation 
from the memoir on Equisetum may appropriately be in uced ih 
this point: “But Srur has shown that in the Ostrau beds, pas*’ 
from the lower to the higher strata, a series of forms, — 
ramifer Stur, C. cistiformis Stur, C. approximatiformis Si 
C. ostraviensis Stur, represents transitions from the 
ment of Archeocalamites, represented in pl. 1, fig. 15, to that 
