1 66 
Blackburn.— On the Vascular Anatomy of 
Text-fig. 9. 
Clematis orientalis. 
Hypogeal form, x§. 
seems correlated with an earlier development of foliage leaves. The first 
few pairs of leaves in the hypogeal form are frequently reduced to minute 
concrescent scales (see Text-fig. 9). The scale leaves fre- 
quently supply only one strand to the vascular cylinder, 
and the internodal strands may be reduced to three. 
C. Flammula. The cotyledons are epigeal (see 
Text-fig. 10). There is a tendency to increase the number 
of vascular bundles to five or six in some of the inter- 
nodes, otherwise it is similar to C. recta. 
C. viticella is of the hypogeal type and is remarkable 
in having three strands to its cotyledons. The lateral 
strands are inserted in the gaps between the three 
plumular strands on each side, and for a short distance 
a tetrarch arrangement is present. The intercotyledonary 
poles soon die out and a diarch root is formed (see 
Thomas, loc. cit., p. 70 6). 
C. Hendersonii and C. integrifolia resemble C. viti- 
cella. 
As a result of his careful study of the genus Clematis , 
Sterckx was led to the conclusion that the opposite-leaved 
form has been derived from a form with leaves arranged 
on a spiral phyllotaxy of two-fifths. An investigation of 
the seedlings of the genus led the writer independently 
to the same conclusion. The considerations on which 
this hypothesis is based are as follows : 
(a) The phyllotaxis of C. Vitalba in the seedling is 
two-fifths, and only after the formation of about fifteen 
foliage leaves is the opposite and decussate arrangement 
arrived at. This seems suggestive on the basis of the 
principle that ontogeny repeats phytogeny. 
(b) The opposite leaves and long internodes, possibly 
correlated with the climbing habit, are not found elsewhere 
in Ranunculaceae, whereas the two-fifths phyllotaxy and 
relatively short internodes found in the seedlings of 
C. Vitalba , C . Davidiana , and C. alpina are characteristic 
of the seedlings of this order, and this leaf arrangement is 
usually maintained in the adult plants. 
(e) In the flower, a notably conservative part of the 
plant, although the sepals are opposite, the stamens and 
carpels are spirally arranged. 
The consideration of these points, in default of evidence to the contrary, 
would seem to justify the conclusion that the genus Clematis is derived from 
some form similar to that found in other members of the order, and 
Text-fig. 10. 
Clematis Flam- 
mula. x 
