604 Worsdell. — Anatomy of Stem of Macrozamia 
which occurs in the stems of Cycas and Encephalartos is also 
to be found in the stem of this plant, though somewhat less 
marked here than in the above two genera. 
The following are the main facts of the general structure : — 
There is a large pith occupying half the diameter of the stem. 
Outside this is the normal vascular ring, consisting of about 
equal thicknesses of wood and bast. Immediately outside 
this is a similar ring of the same thickness, constituting the 
first anomalous zone. Immediately following this again is 
a third ring, consisting of very much smaller and more widely 
separated segments or bundles. This third ring is finally 
succeeded by a fourth series of segments, which, however, are 
developed only here and there, and for the greater part of 
the circumference of the stem are absent (Fig. i). This 
structure is figured from a still larger stem (of M. Moorei , 
F. Muell.) in the Kew Museum. 
This is what is usually seen in the lower region of the stem. 
Higher up, and especially near the apex, the third and fourth 
rings become more and more indistinct, and finally are no 
longer recognizable. The first anomalous ring alone persists 
as a conspicuous zone close to the apex of the stem. 
I will now proceed to describe in detail the various tissues 
which go to make up the stem of this plant. 
Structure of the Pith. 
One of the most striking features of the whole structure, 
and one which is apparent at the first glance, is the presence 
in the pith of a dense network of vascular bundles, in fact the 
same phenomenon which occurs in the stem of Encephalartos , 
but which has been found to be absent in all other genera 
hitherto described. 
If transverse sections are made in any portion of the pith, 
these bundles will usually be found in oblique or even in 
longitudinal section, but are scarcely ever cut through in an 
accurately transverse direction, showing that they do not run 
as isolated bundles perpendicularly through the tissue of the 
