CYATHEAE 607 
by a diagrammatic figure (Fig. 338), but with the reservation that the rapidity 
with which the successive stages are passed through varies considerably: it 
is believed, however, that the diagram will serve to represent the course 
of development of the vascular system, not only in the Cyatheae, but also 
in most of the solenostelic and dictyostelic Ferns, up to the particular 
stage that they retain when mature. The following description is taken 
almost verbally from Mr. Gwynne-Vaughan’s memoir. 
The young plant of A/sophila excelsa has its leaves arranged radially 
all round the axis. At the very base of the stem the single central 
Fic. 337 C. 
Cyathea Imrayana, Hook. Piece of stem with four leaf-bases, after removal of the 
outer layers of cortex, seen from without. The margins of the four leaf-gaps, the bundles 
which spring from them and pass into the leaves, the roots inserted on them (black), and 
the bundles which run down within the cortex are exposed. The cortical bundles and 
root bases are quite free, the rest are covered by semi-transparent parenchyma. Natural 
size. (After De Bary, from Engler and Prantl, Vat. Pfanzenfam.) 
cylinder possesses a small central strand of xylem, usually with a few 
xylem-parenchyma cells intervening between the tracheides. The first leaf- 
trace may depart without in any way altering the structure of this stele, 
or of its xylem-strand, but usually the phloem on the adaxial surface of the 
leaf-trace is prolonged a short distance downwards into the substance of 
the central xylem. At the departure of the subsequent leaves this feature 
is much more pronounced, and the phloem thus decurrent runs down 
through the whole length of the internode to meet with that decurrent 
from the leaf below. In the second leaf, however, it often falls short of 
the point of departure of the first leaf, and ends blindly in the internode. 
