660 Proceedings of Royal Society of Edinburgh. [sess. 
arrows in fig. 17 (a) mark the original position of these larger 
bundles.) 
In every case the bundle reaches its greatest development just 
as it leaves the stele for its respective leaf. 
Lestiboudois,* in a paper on vascular anatomy, figures and 
describes among others the hypocotyl of Ricinus communis. He 
mentions the eight cotyledon traces of the hypocotyl, and refers to 
the bundles a, b, c , etc. (fig. 8), as belonging to the first pair of leaves, 
but does not mention their branching, and he apparently considers 
continuations of the cotyledon traces to pass on upwards to the 
epicotyl. The rest of his remarks, which are almost impossible to 
follow and understand, is concerned with the arrangement of the 
epicotyledonary bundles, to allow of a phyllotaxy of -f above the 
first pair of leaves. 
Arrangement of Bundles in the Embryo. 
To determine at what stage in the development of the plant 
these foliar bundles made their appearance, much younger specimens, 
and finally embryos, were examined. 
The whole of the branching bundle system, described above in 
the fully elongated hypocotyl, was already completed in the 
youngest seedlings examined. In one case (fig. 22) the cotyledons 
were still inside the testa ; the length of hypocotyl outside was, 
19 cm., and inside *2 cm. (A. B. fig. 22). Into this '2 cm. the 
whole course of the branching of the cotyledon bundles was com- 
pressed, the details being exactly the same as those described above. 
Finally, transverse and longitudinal microtome series were cut 
of embryos dissected from the Bicinus seed. 
In the root region of the embryo the tetrarch arrangement of 
the adult plant could be distinguished, and the arrangement of 
vascular elements in the passage from root to shoot, as described 
above, was already laid down, though neither xylem nor phloem 
elements were fully differentiated. In the hypocotyl the eight 
cotyledon traces were distinctly visible, but everywhere the xylem 
and phloem were only distinguishable by the relative size of their 
elements ; it was impossible to make out sieve tubes, and even the 
protoxylem elements were unthickened (fig. 24). 
* Lestiboudois, Ann. cles Sci. Nat. Bot. } vol. x„ ser. 3, 1848. 
