certain Orders of the Ramies . 663 
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PAEONIACEAE. 
For the reasons which have induced me to place Paeonia, usually 
regarded as a member of Ranunculaceae, in a separate, independent order, 
I refer the reader to my article on the subject in the Journal of Botany. 
The vascular structure of the leaves and stem is very much more like that 
of Magnoliaceae than that of Ranunculaceae. 
Paeonia, sp. (herbaceous type). 
Leaf : the petiole contains a horseshoe-shaped arrangement of the 
bundles, consisting of a large median bundle, two large lateral ones 
adjacent to it, and two or three smaller ones at either end of the arc ; in 
the upper part of the organ, owing to the incurving of the bundle-arc, an 
almost complete cylinder is formed (Figs. 19, 20). In the very base of the 
petiole, whose tissues are already in intimate union with those of the cortex 
of the stem, the two (2-4 in some species) large lateral bundles, which 
by this time have become considerably curved in contour, separate off each 
a bundle which rotates on its axis, assuming thereby an inverted orien- 
tation, and takes up a position on the ventral side of the bundle from which 
it separates ; the whole subsequently, by intimate union of the two mutually- 
inverted parts, becomes a concentric bundle, consisting of external phloem 
and internal xylem ; or the ventral may never actually separate from the 
dorsal portion, but the whole strand becomes incurved and finally con- 
centric. From the smaller bundles of the horseshoe, also, minute bundles, 
