160 
PROFESSOR W. 0, WILLIAMSON ON THE ORGANISATION 
Ptadcliffe, and in which the same bifurcation of the secondary pinnules is seen at 
y, y, each branch being supplied with a secondary fibro-vascular bundle o', from 
which a bundle of a third order a" is given off, as in Rachiopteris duplex. This 
mode of dichotomous branching of secondary pinnules is clearly incompatible with 
fronds of the ordinary pinnate or bipinnate types. The plant must have had 
some more distinctive contour. The lowest secondary pinnules of several forms of 
Pteris, e.g., P. umhrosa and P. serrulata branch in this quasi-dichotomous way. 
M. Zeiller has fig'ured in his ‘ Etudes des Gites Minerales de la France.—Bassin 
Houiller de Valenciennes/ two Carboniferous Ferns that distinctly branch in this 
manner, viz., Mariopteris latifolia {loc. cit., Plate XVII., and Diplotemma Zeilleri 
Stur, Plate XVI.). 
The additions I have made from time to time to our knowledge of the organisation 
of the interesting fructincation, Calamostachys Binneyana, have left but few lacunae in 
that knowledge to be filled up. Two points, nevertheless, have as yet been obscure, 
viz., the distribution of the vascular bundles in the central axis of the strobilus and 
the nature of the peripheral terminations of the fertile bracts or sporangiophores. 
Figs. 7 and 8 of Plate 2 throw light on both these points. 
Fig. 7 is a slightly oblique transverse section through an axis of Calamostachys 
Binneyana, in the centre of which, a, is a quasi-medullary cellular parenchyma more 
or less invested by scalariform vessels at h, h'. At the points b, b, these tracheids are 
few in number, but at the four angles b', b' they are much more numerous ; especially so 
in other strobili in my cabinet where such points approximate to the nodes of the axis. 
Fig. 8 represents one of the finest tranverse sections of this Calamostachys 
I have obtained. In it a represents the central axis corresponding to fig. 7. This 
centre is invested by the cortical zone, h. The fertile sporangiophores appeaP at v, 
and their much-thickened peripheral extremities are seen at v . At the points v", v" 
accumulations of tracheids appear. On comparison of this figure with that given 
on Plate 54, fig. 23, of Part XL (‘Phil. Trans.,’ 1881), it will be seen that these 
clusters of tracheids are concentrated in the immediate neighbourhood of the point 
v'" of that figure, i.e., where each sporangium, u, is organically united to the thick¬ 
ened end of the sporangiophore, u'. It thus appears that these peripheral terminations 
of the sporangiojDhores approach even nearer than they were previously known to do 
to those of the living Equisetums, in corresponding parts of which similar clusters 
of tracheids exist. At g, g are transverse sections of the bracts of the next inferior 
verticil of the sterile organs, and at g', eg' tips of a yet lower verticil of similar organs. 
On studying a number of slides prepared for me by my active auxiliary, Mr. 
Isaac Earnshaw, of Oldham, I found in several of them sections of fragments of a 
Z. elli'ptica. In tLe specimens wLich I first described, tbis part of the cortex had inyariahlj dis¬ 
appeared. But I have more recently obtained specimens in which this inner cortex, with its charac¬ 
teristic gnm-canals, is preserved; as is also the case in the specimen described above, where the layer 
in question is indicated by h .—February I2th, 1889. 
