626 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vo.. VI. 
phlceotermal sheath. The external and internal phlceotermas ap- 
parently do not unite through the foliar gap corresponding to the 
cotyledonary trace, probably for the reason that the latter is plugged 
with pericycle. 
The writer believes it inadvisable at the present time to enter further 
into the subject of the development of the central cylinder of the mono- 
cotyledons, since it is somewhat complex and specialized, and, moreover, 
presents a number of interesting features which merit a separate 
consideration. 
CONCLUSIONS. 
As a preliminary to the description of his own observations on the 
anatomy and development of the vegetative axis in the Angiosperms, 
the writer has suggested certain questions to be answered by a renewed 
investigation of the facts. It is now in order to discuss how far the 
study of development and the re-examination of the anatomy of the 
central cylinder of the Angiosperms recorded in the preceding pages 
elucidate the problems suggested in the introduction. 
].—The first question concerns the accuracy of Van Tieghem’s descrip- 
tion of the mode of origin of his polystelic type of central cylinder. As 
has been already stated, he regards the polystelic arrangement of vas- 
cular strands as the result of the repeated bifurcation of the primary 
stele. If the writer’s observations on the development of the central 
cylinder in the Filicales as exemplified by his description of the stelar 
development of Pteris agutlina, are correct, the vascular axis in Van 
Tieghem’s polystelic type develops as a concentric fibro-vascular tube 
perforated by gaps corresponding to the points of exit of the leaf-traces. 
There is consequently no indication whatever of the repeated forking 
of the primary stele. Inthe case of the polystelic Angiosperms, the 
writer’s observations on the Primulaceew, Halorhagidaceze and Saxifra- 
gacez, as well as those of Gwynne-Vaughan on the Primulacee, go to 
show that here also there is no indication of the repeated bifurcation of 
the epicotyledonary stele, but that the latter gives rise to a tubular 
central cylinder characterized by lacune subtending the points of exit 
of the foliar strands. It would appear that Van Tieghem has failed to 
notice the extremely important influence of the leaf-traces on the con- 
formation of the central cylinder in the Filicales and Angiosperms.: 
Had he devoted more attention to the subject of development, this 
important feature could hardly have escaped his observation. 
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