368 Boodle . — Anatomy of the Schizaeaceae. 
runs obliquely into the base of the leaf-trace, while the other 
arm is directed longitudinally forward in the stele. In this 
way the junction of the xylem of petiole and rhizome 
is effected. One of these nodal tracheides isolated by 
maceration is shown in Fig. 6. They occasionally have 
a more complicated and irregular form. Similar branched 
tracheides occur at the division of the stele when the stem 
dichotomizes. 
In the petiole of Z. dichotomum as in Z . japonicum the proto- 
phloem forms a nearly continuous ring. The biggest sieve- 
tubes of the metaphloem and the greatest thickness of phloem 
occur in the three bays of the xylem. Spiral protoxylem- 
elements are present on the lower side of the xylem-mass. 
Examination of a young stage of the petiole proved that in 
the region, where the upper side of the xylem is rounded 
(without a median bay), two protoxylem-groups consisting 
of spiral elements on the lower side of the xylem were the 
first to differentiate. A good deal later two to three groups 
of * protoxylem,’ consisting chiefly at any rate of scalariform 
tracheides, were differentiated at each side of the xylem-mass, 
in the regions corresponding to the lateral prominences. 
Then subperipheral and peripheral tracheides were formed 
on the upper and lower sides, the elements opposite the two 
bays being late in differentiation. The development of 
tracheides in the interior is rather irregular, but appears to 
depend partly on the size of the mature elements to be formed. 
Siliceous nodules with a granular texture are fairly numerous 
in the xylem-parenchyma. 
L . pinnatijidum has a petiole of the same type as the last 
species, but the bundle is smaller. The development is 
evidently fairly similar. In the region where the upper side 
of the xylem is rounded there are four protoxylem-groups, 
two on the lower side and two lateral. Their differentiation 
is probably more nearly simultaneous than in Z. dichotomum. 
In L.scandens the xylem of the petiole has a more rounded 
form than in the species described above. There are three 
protoxylems, one on the lower side and two lateral. Some 
