~~ 
1898-99.] |. MORPHOLOGY OF THE CENTRAL CYLINDER IN THE ANGIOSPERMS. 623 
Through the kindness of Mr. Jackson Dawson, of the Arnold Arbore- 
tum of Harvard University, the writer has had the opportunity of study- 
ing the anatomy of a number of seedlings of Melumbium luteum. The 
first root in this species is abortive, so that in aseries of sections through 
the base of the young plant, one passes almost immediately into the coty- 
ledonary region. The very short, pithless central cylinder of the young 
axis becomes tubular immediately below the level of exit of the coty- 
ledonary traces. The exit of the latter breaks the stelar tube into four 
segments. Photograph 10, plate 8, shows the disposition of the stelar 
system just above the point where the cotyledonary traces have passed 
off. One cotyledon, coz., is present; the other has been broken off. The 
four cotyledonary traces anastomose outside the lacunar cortex and the 
resulting network gives off the cotyledonary strands proper, as well as a 
series of strands which run through the cortex of the first internode. 
Photograph 24, plate 10, represents a section through the first internode ; 
a are the four primitive fibro-vascular strands ; 7 are the cortical strands. 
At the second node, the four central strands again form a tube from _ 
which a number of functional roots are derived, as well as strands for the 
third leaf. The exit of the latter causes a breaking up of the stelar 
tube once more into segments, which are henceforth more numerous 
than four. The cortical strands likewise send off contributions to the 
third leaf; they have, however, no connection with the strands of the 
roots originating from the second node. The latter, as is the rule in 
both Cryptogams and Phanerogams, unlike the leaf-traces, do not sub- 
tend any gaps in the original central cylinder. 
MONOCOTYLEDONS. 
The orders hitherto discussed belong to the dicotyledonous Division of 
the Angiosperms. Astely so-called is of comparatively rare occurrence 
in the present group for reasons which will be subsequently suggested. In 
this division, as well as in the Dicotyledons, a study of the development 
of the stelar system seems to throw considerable light on its morphology. 
The writer does not propose in the present memoir to more than touch 
on the development of the central cylinder in the Monocotyledons, be- 
cause that subject appears to him to be of great importance from the 
standpoint of the phylogeny of the group at present so much in dispute, 
and for that reason it seems advisable to devote a special memoir to 
the development of representatives of the various monocotyledonous 
orders. 
Van Tiezhem mentions Pista stratiotes among the Aroids as possess- 
