6io Worsdell. — Anatomy of Stem of Macrozamia 
the normal ring abuts on the innermost tracheides of the first 
anomalous ring, an additional anomaly was perceived, which, 
in previous examinations of similar structures, had been 
entirely passed over. Here, between the two rings, a tertiary 
cambium had arisen, whose activity had produced a single 
small and isolated bundle, the peculiarity of which, how- 
ever, lay in the fact that the orientation of its parts was 
reversed, its phloem being directed towards that of the 
normal ring and its xylem towards that of the anomalous 
ring (Fig. 9 avb‘ d ). 
Owing to the expansion of the phloem-parenchyma of the 
normal ring, some of the phloem-elements, such as the fibres, 
were seen lying outside the little bundle, which latter had 
thus become partially embedded in the phloem, and also, by 
the pressure of the parenchyma, rather distorted and shape- 
less. In sections of the same region from other parts of the 
stem a similar small bundle was observed, but with a different 
orientation, as it lay sideways, the plane of symmetry of its 
collateral structure forming a right angle with that of the two 
rings. In another case it was observed to lie, with the normal 
orientation, in a medullary ray at the side of the segments, 
but still in the region between the two rings. But I look 
upon these last two positions as departures from the normal 
orientation of the bundle, being irregularities due, probably, 
to the pressure of the surrounding parenchyma ; much the 
more usual position is the inverted one above described. In 
other parts of the stem this cambium was seen to be less 
active than in the cases just described, and to form fewer 
elements of xylem and phloem, so that the tiny bundles thus 
formed are scarcely perceptible. Again, where a segment 
of the first anomalous ring is but feebly developed and but 
very few xylem- and phloem-elements are formed (for in 
certain parts of the stem this anomalous zone may be broken 
up into comparatively small segments), immediately on its 
inside, only separated from it by a few large parenchymatous 
cells, is frequently seen a minute bundle, or rather a half- 
bundle, consisting of two or three radial rows of phloem- 
