ANATOMY 401 
The leaves appear both from their size and from their structure 
to have been the assimilating organs, while the axis took little part in 
that function. Their parenchymatous tissue was, however, mechanically 
strengthened by bands of sclerenchyma. ‘The vascular strands given off 
at the nodes usually branched within the cortex of the stem into strands 
which passed out as the veins of the leaf, though in some cases a single 
strand entered the leaf. 
Sphenophyllum insigne. Transverse section of rather young stem, showing triangular 
primary wood with a canal at each angle, marking the protoxylem, then secondary 
wood, remains of phloem, and the primary cortex showing two of the furrows. about 
30. Froma photograph, PA. Trans. W. and S. Will. Coll., 919. (Block from Scott's 
Studies in Fossil Botany.) 
The strobilus of Sphenophyd/um was constructed on a plan similar to 
that of the vegetative shoot, with slight structural differences, and with 
the additional fact that the spore-producing parts are present. These took 
the form of sporangiophores, resembling in their main features those of 
other sporangiophoric Pteridophytes. The most obvious differences between 
the strobilus and the vegetative shoot are that the internodes are shorter, 
and the leaves, which are elongated as before, frequently show a distinct 
webbing below. The result is that the whole cone appears externally as 
a compact body, with the sporangiophores very adequately protected till 
mature (compare Fig. 215). The various fossils described under the 
generic name of Sphenophyllum show differences of detail in the number 
2c 
