the Anatomy of the Cone and Fertile Stem of Fquisetnm. 455 
2. The vascular system of the cone of E. debile is much reduced 
and forms a loose irregular network. Frequently numerous parenchyma- 
tous meshes originating below the cone persist for a considerable distance 
into the cone, some of them even traversing the whole cone. 
3. The stele of the cone of E. variegatum is also of a somewhat reduced 
type. 
4. On grounds of comparative anatomy the separation of protoxylem 
and metaxylem in the internodes of the cones of certain species of Equisetum, 
a condition most marked in E. maximum, is regarded as a derivative 
character, due chiefly to reduction of the radial extent of the metaxylem. 
5. It is concluded that a comparative study confirms the view already 
put forward that parenchymatous meshes of the cone probably first arose, in 
the pliylogeny, at points vertically above the departure of the traces of 
sporangiophores, though at a certain height above this level. They were, 
therefore, not true gaps, as defined by Jeffrey. In the cases in which 
the meshes arise very close above the departure of the trace, this approxima- 
tion is probably due to reduction of xylem during the phylogeny. The 
primitive system was probably siphonostelic. 
6. The following points in the anatomy of E. sylvaticum support the 
view that the insertion of the annulus marks the position of a vestigial 
node : (a) the numerous anastomoses of the axial strands at this level ; 
(b) indications of anastomosis of the protoxylem at the same level ; (e) the 
presence in the axis opposite the annulus of Cone B of an abortive trace that 
never becomes free ; ( d ) the presence in this same cone at the level 
of insertion of the annulus of tracheides somewhat resembling those of the 
nodal xylem of the vegetative axis ; (e) the occurrence, according to Milde, 
of branches below the annulus. 
7. In one of the cones of E. debile four small groups of vascular cells 
were observed in the parenchyma of the annulus. Though they are 
unconnected with cells of the axial bundle it is possible that these vascular 
cells represent vestiges of the traces of the annular node. In this species, 
however, and still more in E. variegatum , there are but few indications 
of the former presence of a node at the insertion of the annulus. 
8. In some specimens of E. debile the ring of nodal or (supranodal) 
xylem is not complete at the level of the uppermost whorl of leaves. 
My thanks are due to Professor F. W. Oliver, F.R.S., in whose 
laboratory the present investigations were carried out, not only for his 
continued help and encouragement, but also for material of E. vai'iega- 
tum . Major T. G. Hill, A.R.C.S., most kindly gave me the benefit of 
his advice on certain points of technique. I also wish to thank Dr. 
Shriv Yam Kashyap, who sent me from India a most generous supply 
of the cones of E. debilc , of all sizes and ages ; and Miss Agnes Fry, who 
supplied me with cones of E. sylvaticum. 
