Catamites and Dicotyledons . 141 
shows the structure of the woody cylinder of a biennial stem 
of this species a little below the region of a medullary 
diaphragm. It is evident that the continuity of the woody 
zone is interrupted at approximately equal intervals by 
broad parenchymatous bands running from the persistent 
zone of medullary tissue just inside the fibrovascular cylinder 
to the cortex. Photograph 4, PL VIII, represents one of these 
parenchymatous organs more highly magnified. Certain 
dark-walled elements may be distinguished among the paren- 
chymatous cells ; these are moribund cells corresponding 
to those of the fistular portions of the pith. In Photograph 5, 
PL VIII, is to be seen a radial section through one of these 
parenchymatous organs. The zone of secondary wood main- 
tains its full thickness above the organ, while below it 
becomes narrower in passing upwards. On the right above 
is the medullary diaphragm. Photograph 6, PL VIII, shows 
the parenchymatous organ more highly magnified. Externally 
is to be seen a layer of periderm. Certain of the cells of 
the parenchymatous organ are dead, and show dark in the 
photograph. On the lower side of the parenchymatous organ 
a leaf-trace may be seen passing upwards and outwards. 
Photograph 7, PL IX, is of a tangential longitudinal section 
of the nodal region of the woody cylinder. Two parenchyma- 
tous organs are to be seen, and at their lower margins 
may be made out two corresponding leaf-traces in oblique 
transverse section. The parenchymatous interruptions of the 
woody cylinder illustrated in the photograph described above 
occur always opposite the leaf-traces and a little below the 
medullary diaphragm. They cause the only breaks in the 
continuity of the woody zone, and are, as the writer will 
attempt to show subsequently, to be regarded as the upper 
ends of the foliar lacunae which have not been closed up by 
the formation of secondary wood. 
Cicuta maculata is another marsh-plant with numerous 
leaf-traces passing out in the nodal region, and with a con- 
siderable secondary growth of the ligneous zone. Photo- 
graph 8, PL IX, represents the nodal region of a woody 
