620 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VoL. VI. 
paragraphs of the development of the stelar system of Ranunculus and 
Anemone, will doubtless be struck with the bearing of the facts there 
described, on the problem of the morphology of the central cylinder 
in the Angiosperms. For example, we find in this order that the astelic 
type of Van Teighem does not originate by the sinking in of the 
phlceoterma around the individual bundles, with a subsequent union of 
the individual phlceotermal sheaths to form a continuous external and 
internal phloeoterma, because the fibro-vascular system is, from the very 
first, tubular, and the central cylinder has primitively an internal 
phlceoterma. Further, the stelar system of so-called monostelic species 
of Ranunculus and Anemone appears from a study of the course of 
development to be really an astelic type, in which the internal phloeoterma 
has become obsolete. These two facts, vzz., the primitively tubular 
gamodesmic) nature of the central cylinder in the Ranunculaceze, and the 
derivation of the so-called monostelic medullated type by the degenera- 
tion of the internal phlceoterma, are, in the writer’s opinion, of great 
importance in connection with the view to be taken of the morphology 
of the central cylinder in the Angiosperms generally. Before proceeding 
to consider that subject, however, it will be well to describe the develop- 
ment of representatives of other angiospermous groups, which present 
the phenomenon of astely, so-called. 
NYMPHAACE. 
In his essay on Polystely, Van Tieghem describes the Nymphezacee as 
an order illustrating his astelic type of central cylinder. The 
arrangement of the fibro-vascular strands in the mature stem of the 
various genera of this order is extremely complex, and, on that account, 
it is the more desirable to investigate the development of the stelar 
system in the young plant in order to discover, if possible, what is really 
the primitive condition of the fibro-vascular apparatus in this group. 
The genus Brasenia is probably one of the most primitive of 
the order. In the internodes of the rhizome of the mature plant 
of Brasenia purpurea, there are present two concentric fibro-vascular 
strands, in which the elements of the xylem, as is commonly the case in 
aquatics, are represented merely by air-spaces. The epicotyledonary 
stele of the seedling of Brasenia purpurea is a pithless fibro-vascular 
strand, in which the vessels are not degenerate as in the mature rhizome. 
The stelar system retains the simple character until a considerable 
number of leaf-traces have been given off. The stem, however, sooner 
or later becomes relatively massive, and the fibro-vascular system 
