certain Orders of the Ranales. 
66 1 
both at the base of the main blade and in the stalks of one or two of its 
subdivisions, a very small inverted bundle occurs on the ventral side of one 
of the arc-bundles. By means of these phenomena we are able to see the 
relationship between the leaf-structure of this species and of those which 
possess a cylinder. 
Clematis Vitalba , L. 
Leaf: In the typical part of the petiole a complete cylinder of bundles 
obtains. 
Clematis heracleifolia , DC. 
Leaf : In the typical region of the petiole is a wide arc of 12-13 
bundles. On the ventral side, and some little distance away, are about four 
very small inverted bundles (Fig. 14). In passing either upwards to the 
lamina or downwards to the leaf-base, two of these bundles fuse together 
to form a strand, which then, revolving on its axis, unites with a bundle of 
the dorsal arc ; the two other ventral bundles die out in situ. 
C. recta , L. 
Leaf: Extending throughout the petiole is the following structure: 
a dorsal arc of about eight bundles, varying in size. The petiole, as also in 
the last species, has a deep groove on the ventral face. On either side 
of this groove are, respectively, one and two minute inverted bundles, 
evidently on the point, phylogenetically speaking, of dying out altogether. 
Before the dorsal arc unites with the stem-cylinder, these ventral bundles, 
which extend almost to the very base of the leaf, disappear, but I did not 
determine whether they die out in situ or unite with the dorsal bundles. 
C. apiifolia , DC. 
Leaf'. In the typical part of the petiole is a complete, almost circular 
cylinder of bundles ; lower down a flattening occurs on its ventral side, and 
the bundles thereof begin to pass across and unite with those of the dorsal 
side ; one or two of the more lateral ones persist to the extreme base of the 
petiole before finally uniting with their dorsal neighbours immediately 
before the latter unite with the stem-cylinder. By eventual lateral fusion 
the latter receives three main bundles from the leaf: a median and two 
•lateral ones. 
C. alpina , Mill. 
Leaf \ This is an advanced type from the point of view of its anatomy, 
inasmuch as the primitive petiolar cylinder has become practically extinct, 
so that in both the uppermost and lowermost region merely a dorsal arc of 
bundles obtains ; in an intermediate region, however, traces of the ancestral 
cylinder can be, at least in some leaves, discerned in the form of a minute 
ventral bundle with inverted orientation lying near one of the end-bundles 
of the arc from which it had presumably become detached (Fig. 1 5). 
