160 Blackburn. — On the Vascttlar Anatomy of 
the two strands are inserted in the vascular ring at the same level. Cambial 
growth begins at a somewhat earlier age in this species (see PI. XIII, 
Fig- 3)- 
D. luzulinutn differs from D. Occident ale only in that the first foliage 
leaf has one lateral strand. 
D. Ajacis is an annual and differs in several important points from the 
species described above. Its foliage leaves are produced much more 
rapidly, so that a seedling of the same age would have many more foliage 
leaves than that of another species. The leaf bases are not sheathing. 
The bundles in the vascular ring are more numerous than in the other 
species. This is probably correlated with the greater production of leaves. 
Secondary thickening arises much later and is probably less in extent. 
There is a relatively large pith. This feature seems to be correlated with 
the larger number of bundles in the vascular cylinder. In one seedling the 
first foliage leaf supplies only one lateral to the ring, the other fusing 
with the median bundle. The central and, if present, the lateral strands of 
the first foliage leaf join the vascular ring at the same level as the cotyle- 
donary traces. At the cotyledonary node there are a large number of 
plumular bundles. Stem structure persists for some way down the hypo- 
cotyl, differing only from that of the epicotyl in the presence of the two 
‘ mesarch ’ protoxylem groups derived from the cotyledons. The bundles 
gradually close up and the number is reduced till the usual six strands, 
three on either side of the cotyledonary plane, are reached. By reductions 
of the pith and closing up of the plumular tissue, root structure is established 
as in the other species, but at a much lower level in the hypocotyl. 
Helleborus . H. foetidus is described by Marie as having ordinary 
dicotyledonous structure in its stem. That is to say, it has a ring of 
bundles connected later by cambial growth. 
The genus is noted for having a sinuous endodermis dipping down 
between the bundles. 
The seedlings and young plants examined showed a noticeable simi- 
larity in all the nodes except the cotyledonary node. 
Each leaf supplies three strands to a somewhat slender vascular 
cylinder, but sometimes one or both laterals are missing in the early leaves. 
The cotyledonary node is quite normal and possesses a pith which persists 
a short way down the hypocotyl. 
Nigella. The vascular system of the adult stem consists of a ring of 
strands varying in number and size. Cambial growth may be found at the 
base of the plant in some species. The seedling structure is similar to that 
of Delphinium Ajacis y but differs in a peculiar distinctness of the individual 
bundles. 
N. hispanica. A meristematic ring does not appear till a very late 
date, and then it is only in the region of the cotyledonary node. The 
