Phloem in the Stems of Dicotyledons. II. 
439 
Leaf. 
In the midrib the scattered arrangement of the bundles is very evident 
The largest bundle is situated by itself on the dorsal side. Farther to the 
ventral side is an arc of fairly large bundles, the terminal ones of the arc 
being at the inner coiners of the midrib. Unevenly distributed in the 
remainder of the space to the inner side of the arc are eight or nine very 
much smaller bundles of varying sizes, three or four of which on the extreme 
ventral (adaxial) side are very rudimentary and almost extinct. The small 
medullary bundles are orientated like those of the arc. We thus see that 
the medullary strands of the leaf are better developed and less reduced 
than those of the stem, the latter having completely lost their xylem, while 
the former have retained it. This is another piece of evidence in favour 
of the leaf-structure representing the ancestral type. The very rudimentary 
strands on the extreme ventral side of the midrib may represent the reduced 
adaxial portion of the original cylinder. 
Taraxacum officinale, Weber. 
Peduncle. 
The vascular ring consists of three sizes of bundles, all practically in 
a line, representing, as in so many of such cases, the original scattered 
triserial arrangement which existed before the advent of the wide lacuna 
of the pith. 
- Leaf 
The above-stated view, that in the stem (or peduncle) of this plant, 
and of all Cichoriaceae, there was an aboriginal scattered system of bundles, 
is confirmed by the structure of the leaf. Here, around the central lacuna, 
are a large number of very scattered strands of which only a few (3-5) near 
the edge of the lacuna on the dorsal side are well-developed bundles ; lying 
between and to the outside of these last are considerable numbers of widely- 
distributed and, in many cases, exceedingly small and rudimentary phloem- 
strands of obviously vestigial nature. 
Cynaroideae. 
Cynara Cardunculus, L. 
Stem. 
This is one of the Compositae in which the scattered arrangement of 
the bundles is most pronounced. The vascular ring consists of this complex 
system, many of the bundles being inversely orientated, others orientated 
sideways. They are of all sizes : some extremely small, others reduced 
to mere rudiments and fragments. One or two of the large inverted bundles 
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