292 
PROFESSOR W. C. WILLIAMSON ON THE ORGANISATION 
like Plate 21 , fig. 4, C, seem to indicate some disposition on the part of these phloem 
tubes to arrange themselves in radial lines. 
Radial sections of the inner cortex (Plate 23, fig. 9, p) exhibit no peculiarities in 
the form and arrangement of its parenchymatous cells requiring special notice, except 
one shortly to be referred to. It is otherwise with the outermost cortex r, of part of 
which a longitudinal section, enlarged 31 diameters, is shown in Plate 22 , fig. 11 . 
The peripheral layer is wanting in this preparation. It shows, however, at r, r, the 
coarse parenchyma seen in the section, Plate 22 , fig. 2 . It also exhibits three thick 
bands of sclerenchyma (Plate 22 , fig. 11 , t, t, t) corresponding to the detached patches 
of the same tissue seen in figs. 1 , 2 , and 8 . The cells forming these horizontal bands 
have a mean diameter of from ywoo — ' 000 G 2 to tooo = '0005 of an inch. One 
longitudinal section in my cabinet exhibits one of the twin vascular bundles already 
described (fig. 8 , u, u) passing upwards and outwards through the cortex. 
Plate 23, fig. 12 , is a tangential section through the exogenous xylem of a stem or 
branch which is giving off a true branch, w. We have the xylem zone at B, a little 
of the phloem at C ; the inner cortex at p, and the outer cortex at r, with three of 
the horizontal masses of sclerenchyma at t, t, t. The section has not been made 
exactly parallel with the axis of the main stem ; hence it has cut obliquely through 
the considerable branch at w. This branch has evidently originated in a tortuous 
deflection of the xylem vessels, which have only attained to their normal arrangement 
in regular radiating laminae in the more external semi-diameter of the branch. The 
complete development of these radial vascular laminae would only be attained at a 
higher point of the branch where it became entirely free from the parent stem. The 
identical development of a similar branch of Kaloxylon Hooheri is shown in Plates 6 
and 7, figs. 32, 33, and 34 of my Memoir, Part YII. (‘Phil. Trans.,’ 1876). The 
branch, w, of fig. 12 is invested by an imperfectly preserved layer, p , of the inner 
cortical zone. The figure is enlarged 13 diameters. 
The resemblance in the origin of the branch just described to that of Kaloxylon 
Hookeri is also further sustained by the specimen represented in Plate 22 , fig. 13. 
In figs. 32 and 33 of the Kaloxylon referred to above, the branch is seen to be given 
off opposite to a large primary medullary ray; the twm vascular wedges bounding 
that ray on its two sides contributing equally their supplies of vessels and cells to the 
formation of the branch. Fig. 13 exhibits identical conditions. In it we have the 
large primary medullary and phloem ray, n, bounded on its two sides by the lateral 
vascular laminae of the two vascular wedges, c, c. A mass of tracheids and vessels, 
e, e', is being given off from the peripheral angle of each of these two wedges; these 
meet beyond the outer boundary of the primary phloem ray, n, where they unite to 
form the rudiments of the branch, w. The abundance of short tracheids at this point 
reminds us of the similar development of these elements where roots or branches are 
being given off by the stems of living vascular Cryptogams. 
There yet remains to be considered the character of the vessels and tracheids which 
