678 Worsdell. — A Study of the Vascular System in 
between the two has occurred but not the complete revolution of the ventral 
bundle, and union of both sides of each bundle obtains to form the concen- 
tric structure as we see it. In the cortex of some Magnoliaceae all 
transitions towards the completion of this union may be observed — per- 
fectly concentric, three parts concentric, and both normally and inversely- 
orientated collateral bundles being present (Text-fig. 3). Some of these 
latter, as is also the case in Paeoma , die out in the lower part of the 
internode without ever taking part in the union with other bundles to form 
the leaf-traces which unite with the stem-cylinder. In the peduncle of 
Magnolia Sotdangeana is an outermost rank of very small and variously, 
but for the most part, inversely-orientated and rudimentary bundles, which 
doubtless, although I did not trace them, die out below ; they had probably 
emanated from the sepals. Both in Magnoliaceae and Paeonia the con- 
centric bundles are much more typical and in evidence in the peduncle than 
in the stem. 
After a minute and careful study of the vascular system of the orders 
now dealt with, I am prepared to affirm without 
much hesitancy that the inverted cortical bundles 
of Calycanthaceae (allied as this order is to the 
two others immediately concerned) are nothing 
more than the homologues of the inverted bundles 
above described which occur in the cortex of 
Paeonia and Magnoliaceae^ and which represent 
portions of the ventral half of the petiole-cylinder. 
Instead of, as in the case of Ranunculaceae, 
Magnoliaceae, and Paeoniaceae, these ventral 
bundles either uniting with the dorsal strands 
of the leaf-cylinder or dying out in the internode 
of the stem, two of them from each leaf 1 persist 
in an enlarged form as independent cortical 
bundles in the stem, never passing into the central cylinder. In the cortex 
of the peduncle , however, concentric bundles occur, and we may interpret 
them morphologically as being due to incomplete fusion between the 
dorsal and ventral bundles of the leaf-cylinder. 
The proof that the cortical bundles of Calycanthaceae are homologous 
with the inverted cortical bundles of Magnoliaceae, the meaning and origin 
of which we know, is afforded by the peduncular structure of both orders, 
a glance at which is enough to convince us that this peduncular structure 
in both orders is homologous throughout, both as regards the central cylinder 
and the concentric and other cortical bundles. As in the case of each of the 
petiolar concentric bundles of Paeonia , each cortical bundle in Calycanthaceae 
is derived (but phylogenetically , not ontogenetically , as we shall see directly) 
1 i.e. morphologically speaking. 
Text-fig. 4. — Schematic re- 
presentation showing the petiolar 
vascular structure of Calycan- 
thaceae. vb = bundle of ventral 
portion of primitive cylinder. 
