510 Shove.—On the Structure of the 
Marattia only in having from four to five zones instead of 
two ; the plan of compensation from zone to zone is identical. 
The general scheme of the arrangement of the vascular 
tissue in Angiopteris is most clearly conceived by considering 
it in connexion with the insertion of the leaves. The leaf- 
bases, which are set in a rough spiral on the stem, show in 
their lower parts a meshed segment of vascular tissue having 
the form of part of the surface of a cylinder. This segment 
passes from the leaf-base into the outermost zone of the stem, 
uniting right and left with the strands of this zone. Then 
continuing in an obliquely descending direction, it passes on 
into the second zone, and so on until it reaches the longi¬ 
tudinal axis of the stem, where it unites with other former 
leaf-trace bundles and loses all individuality. 
' Since the leaves are set so thickly on the stem, there 
is very little vascular tissue that can be definitely stated 
to belong to the outermost zone; in fact, any part of the 
outer vascular tissue is more truly considered as forming 
the lower strands of the leaf-bundles on their way to the 
interior, than as a portion of a definite meshed cylinder. 
A transverse section of the extreme tip of the base of the 
stem (Fig. 13) shows one large central stele (s); this, at a 
distance of about half a centimetre from the end, bifurcates, and 
by further division of the strands thus produced an irregular 
network arises. It should, however, be remembered that the 
base of the stem has suffered an unknown amount of denuda¬ 
tion, hence the vascular tissue here described forms only part 
of the original system. 
Figs. 13-18 show a series of transverse sections of the stem 
taken at distances of about half a centimetre. 
The steles are seen to undergo frequent division, and are 
scattered irregularly through the section ; only towards the 
end of the series does the grouping into concentric circles 
make itself apparent. Numerous roots (r) are seen to traverse 
the stem, but their places of origin are, with a few exceptions, 
not shown, owing to their position higher up in the stem. It 
should be noted that the roots reach the periphery of the 
