the Anatomy of the Cone and Fertile Stem of Equisetum . 433 
differentiation of the metaxylem in these cones would have led to a 
further closure of parenchymatous meshes. In the reconstructions of the 
steles of Cones B and E of this species the phloem, where it projects be- 
Cone A of E. debile. Axial xylem black ; traces and 
parenchyma white ; protoxylem a broken line enclosing 
a dotted surface; i.a., level of insertion of annulus. 
x 'Zb 
Text-fig. 4. Reconstruction 
of immature stele of Cone B of E. 
debile. Axial xylem black ; traces 
and parenchyma white. The broken 
line enclosing a dotted surface repre- 
sents the outline of the phloem, 
where the latter projects beyond 
the xylem ; i.a., level of insertion 
of the annulus, x 20. 
yond the xylem, is shown by a broken outline, enclosing a dotted sur- 
face. The actual phases represented in the diagrams in no way correspond 
to a natural pause in the differentiation of the xylem. The transition 
from protoxylem to metaxylem is here very gradual. 
