1 62 
Blackburn. — On the Vascular Anatomy of 
the upper and larger leaves. In the peduncle there are five or more distinct 
collateral bundles surrounded by a lignified pericycle several cells thick. 
At the region of the insertion of the leaves the bundles have been 
connected up by secondary thickening so as to form a continuous cylinder 
only broken by the entry of leaf traces, three from each leaf. 
The seedling of this plant is exceedingly small, with tw r o minute sessile 
linear cotyledons. The first few leaves are similar and scarcely larger. 
The anatomy of very young seedlings conforms to the general type for the 
order. It does so in spite of its minute size owing to the very small 
elements of which the tissues are composed. The foliage leaves have each 
three strands, and, owing to the extreme telescoping of the axis, the traces 
of several leaves are present in the axis at the same time, and the strands of 
adjacent leaves may fuse. Secondary thickening begins at a very early 
age, and, considering the ephemeral nature of the whole plant, is surprisingly 
well developed. 
Paeo7iia . The anatomical peculiarities of this genus are largely in 
connexion with the leaf trace. According to Marie, the vascular cylinder 
is of the typical dicotyledonous type with separate bundles connected at an 
early age by secondary thickening. Mr. Worsdell describes concentric 
lateral leaf-trace bundles which pass some way down the stem before fusing 
with the central cylinder, thus forming cortical bundles. 1 
The seedlings are considerably more robust than those of other 
members of the family, and their germination is hypogeal from a large seed. 
P. herbacea. The first foliage leaf is compound in this seedling. The 
cotyledonary node and hypocotyl swell in a tuberous manner at an early 
age, but this is chiefly secondary, being largely due to rapid growth of the 
normal cambium. 
The vascular cylinder, though bulkier, is of the usual type found in 
seedlings of perennials. 
The leaf-trace bundle is very large and fan-shaped and contains much 
secondary tissue. Large buds are present in the axils of the cotyledons, 
and the cotyledonary node is rather drawn out. The pith is persistent and 
flanked by plumular bundles, which are augmented by the half-bundles from 
the cotyledons. 
P. arborea is similar in general structure, though it lacks the tuberous 
swelling at the age examined. The first foliage leaf supplies five strands to 
the stele in place of the usual three. A slight doubleness in the median 
strand of the first foliage leaf is to be observed. 
P. anomala and P. officinalis are similar. In the former, secondary 
thickening appears to be much later, but this may be not so much a question 
of age as of rate of production of leaves, for age is here estimated by 
a number of leaves. 
1 Loc. cit., p. 664. 
