6 1 4 Worsdell. — A natomy of Stem of Macrozamia 
by the presence of a large number of leaf-trace bundles 
and, as in the pith, a network of mucilage-canals whose 
branches penetrate its tissue in every direction. These canals 
are often quite filled with cluster-crystals of calcium oxalate. 
Large stone-cells are of frequent occurrence throughout the 
cortex. The large number of bundles seen in transverse 
section of the stem on the inner margin of the cortex (Fig. i^*) 
represent the inner ends of the girdle leaf-traces as they 
pass obliquely downwards to join the vascular zone. Their 
previous course through the cortex from their origin in the 
leaf-base is identical with that already well known in Cycas 
and other genera. On emerging from the leaf they pass 
for a long distance in the tangential direction, often two or 
three together, close beneath the surface of the stem, gradually, 
however, bending inwards and downwards towards the centre 
(Fig. i f)' Some, however, follow a more direct route and 
bend off suddenly in a radial direction after a longer or 
shorter tangential course and pursue a direct path to the 
vascular zones (Fig. i6 it). These latter, which do not occur 
in every region of the stem, may be associated together in 
considerable numbers, varying in size amongst themselves, 
being branching members of the original single bundle which 
passed into the stem from one side of the leaf-base. As they 
bend off in the radial direction they are often seen to arrange 
themselves in a curious arc, giving the appearance of an 
imperfect little cylinder of bundles, as seen in tangential 
section of the cortex. Some of the larger bundles, which run 
isolated through the cortex, show a distinct tendency towards 
a concentric structure. The leaf-trace girdles, during their 
tangential course around the stem, exhibit a rather striking 
structure from the fact that a large number of the tracheides 
of their secondary wood have become abnormally developed 
so as to resemble, in the spiral thickenings which they 
possess, the ordinary protoxylem. These tracheides are very 
broad elements, having more than twice the diameter of either 
the protoxylem-elements themselves or those of the rest 
of the secondary wood. They are, moreover, like those of 
