672 
Worsdell. — A Study of the Vascular System in 
occurs on the other side of the cylinder, but not quite contemporaneously. At 
the base of the petiole are three bundles arranged in an arc and widely 
separated — a transversely elongated convex median and two arc-shaped 
lateral bundles. 
Cananga odorata, Hook f. 
Leaf'. In the petiole and lamina of this plant (of which I had only 
herbarium-material at my disposal) medullary bundles (3-4 in number) 
occur ; they are approximated to the dorsal arc, as in Magnolia , are orientated 
in the same way as the bundles of the arc, and do not occur far away from 
it ; they have a distinct tendency to assume a concentric structure, with 
central phloem (Fig. 40). This is the only case I observed of medullary 
bundles in the leaf of Anonaceae, and is, therefore, extremely interesting 
and important. Guillard observed the same phenomenon and it was his 
note which suggested my own investigation. 
In th peduncle of Uvaria N arum, DC. 1 , the bundles of the cylinder are 
irregular in position and size, each with a large sclerotic dorsal cap. The 
bundles are arc-shaped. The pith is full of minute, rudimentary bundles, 
each consisting only of a circular phloem and no xylem ; in one place near 
the cylinder is a transitional form between these medullary bundles and 
those of the cylinder in the form of a bundle having its phloem partially 
enclosed by xylem ; another small bundle, with a very small group of 
vessels, was approximated to, and lying at an angle with, a bundle of the 
cylinder (Fig. 39). The above facts seem to show that the medullary 
system of bundles is an ancestral or vestigial character which, for some 
reason or other, has persisted in the peduncle while having vanished from 
the stem ; it is probably to be regarded as a relic of the monocotyledonous 
scattered arrangement of the bundles. In a peduncle of this species from 
the Kew Herbarium I could, however, find no trace of the medullary 
bundle-system ; this character may, therefore, vary with the individual ; 
neither does it occur in the peduncles of U. excelsa or U. Kirkii . 
In th peduncle of Melodorum verrucosum , Hook, f., the bundles of the 
cylinder are few, large, and horseshoe-shaped. A few (two or three) 
medullary bundles occur ; they are small, obscure, and of diverse orientation ; 
occasionally one appears at the end of one of the incurved limbs of a large 
bundle of the cylinder . This fact throws light on the reason for the arc- 
or horseshoe-shaped contour of the bundles of the cylinder in this plant 
and also in the genus Uvaria ; it probably arises owing to constant union, 
either in the past or present, between the bundles of the cylinder and those 
of the pith. 
The structure of the leaf in this order shows distinct affinities both with 
1 A specimen of which was obtained from Kew Museum, No. 1. 
