3 i 8 
Notes. 
(and this is the point of my whole note), well-dev eloped centripetal xylem 
occurs, the tracheides composing it extending along the whole tan¬ 
gential face of the centrifugal xylem in considerable quantity. A very 
interesting and important point in connexion with this diploxylic 
structure is the fact that there are two sets of protoxylem, as has been 
also shown for bundles of a similar structure in the sporophyll of 
Cycas , peduncle of Stangeria, &c. One of these protoxylems is 
attached to the centrifugal, the other to the centripetal xylem. The 
significance of the fact is this: that it indicates clearly, in my opinion, 
the derivation of a collateral bundle possessing such a structure from 
a concentric strand of which the phloem, which in the ancestors of 
the plant was attached to the outer side of the ‘ centripetal’ xylem, 
has completely disappeared. This is also my explanation of the 
occurrence of centripetal xylem elsewhere, as in the peduncle of some 
Cycads, and the foliar organs of Cycads and Coniferae. I regard 
Cephalotaxus as the most ancient of the Coniferous genera, and 
therefore, supposing the Coniferae to be derived from some ancient 
Fern-stock, we should expect to find it exhibiting characters in its 
most primitive organs similar to those which we find in Cycads and 
Ginkgo. Now the two most primitive foliar organs of any plant are, 
to my mind, the cotyledon and the ovular integument. In the former 
I have already shown the absolutely Cycadean character of the 
structure of the vascular bundle, with its enormously developed centri¬ 
petal xylem. In the latter a similar diploxylic structure of the bundle, 
as has been shown above, also predominates. Two conclusions may 
be drawn from these facts, viz., (i) That Cephalotaxus is the most 
primitive of the Coniferae; (2) That this genus forms in some 
measure a connecting link between Cycadaceae and Coniferae, and 
helps us to trace, however faintly, a fragment of the line of descent 
of the latter group. 
I am much indebted to Prof. F. W. Oliver, of University College, 
London, for the supply of material for this research. 
W. C. WORSDELL, Kew. 
ON THE PRESENCE OP VERMIFORM NUCLEI IN A 
DICOTYLEDON. —In consequence of the interesting communication 
of Nawaschin and Guignard concerning the fusion of a vermiform 
nucleus with the polar nuclei in Lilium Martagon , I undertook last 
