60 
PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
similar section to the last, but with portions of the leaves of three foliar disks. Thus 
at t we have the bases of those belonging to the principal disk ; at t' we have the 
alternating series of the disk below ; whilst at t" we again have the tips of the leaves 
of the inferior disk but one opposite to t, showing that the leaves fringing the disks are 
arranged in an order equivalent to that of the decussate plan, in which each third verticil 
returns to the disposition exhibited by the first. In both the above figures the disks 
are seen to consist of two kinds of coarse, thick-walled, cellular tissue; broad lines 
leading from the central axis to the base of each leaf ( t ) consist of prosenchymatous 
cells elongated in the direction of the plane of the disk, the intermediate triangular 
spaces being occupied by a coarse parenchyma. In Plate VI. fig. 34 especially we 
observe that the sections of the leaves ( t ') exhibit transverse sections of the same 
elongated prosenchyma. It is of some importance to note that neither in these nor in 
any other similar sections of these disks have I succeeded in detecting either a barred 
vessel or a vacant space which such a vessel may originally have occupied; yet two 
longitudinal sections in my cabinet afford clear proof that Mr. Carruthers is correct 
when he affirms that a very slender bundle of such vessels runs up the centre of each 
leaf, and, to do so, it must have traversed the disk. I have only succeeded in detecting 
their presence in two out of some fifty sections of the fruit under examination, yet they 
once existed in every fruit. At u u in Plate VI. fig. 34, the section has passed out of the 
plane of the disk and intersected two sporangia. There have been fourteen leaves in 
each verticil of this specimen. Plate VI. fig. 36 is a transverse section made in the 
plane of a verticil of sporangiophores : of these there are usually six in each verticil ; 
but in this verticil there are seven, being half the number of the bracts of the 
adjacent foliar disk (Plate VI. fig. 34) ; this numerical relation corresponds with one 
already observed by Mr. Carruthers, though in the specimens examined by him the 
respective numbers appear to have been six and twelve. Mr. Binney’s figures also 
represent his transverse section as possessing six sporangiophores ; but as the foliar 
appendages are not present in the latter sections, we have no evidence as to their 
number. On turning to the vascular axis (fig. 36, c ), we discover a distinct triangular 
structure with concavely truncated angles, thus producing the hexagonal form which is 
ordinarily characteristic of the axis of these fruits. In the present specimen the axis has 
accommodated itself to the accidental modification which has produced seven sporangio- 
phores instead of six, by the angle c' terminating in two arcs instead of one. At the 
first glance this axis would appear to be almost a repetition of that of Asterophyllites 
Daivsoni (Plate V. fig. 29) ; but, as will be seen shortly, this is not exactly the case. 
We find the vascular bundle under consideration separated into a central and a 
peripheral portion. This bundle is surrounded by the vacant space ( g ) representing 
the missing inner bark, external to which we have the outer prosenchymatous bark (Jc) 
arranged in a series of crescentic curves, portions of two of which unite to form the two 
sides of each of the sporangiophores ( v ). In the latter structures the prosenchymatous 
cells of the bark become long, narrow, and parallel-sided, being drawn out at great length 
