PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
VQQ 
OJO 
Plate XXXI. fig. 45 exhibits correctly the general aspect of the dark coloured hori- 
zontal bands, and their relations to the intervening layers of ordinary parenchyma. 
The cells of the former are smaller and more uniform in size, as well as less lax in their 
arrangement, than the latter. The bands are arranged at uniform distances, which 
vary little in different specimens, there being generally about forty-six of these in each 
vertical inch. They do not appear to form absolutely continuous rings in matured 
examples, encompassing the entire stem, though they do so in young shoots. In the 
former case they are frequently interrupted by the vicinity of cortical vascular bundles ; 
but, in addition to this, we observe often in vertical sections the faintly defined margin 
of one of these bands intercalated between two sharply defined ones, indicating that some 
of them at least become merged laterally in the surrounding parenchymatous tissue : 
tangential sections of the same structure also frequently indicate that where a cortical 
vascular bundle approaches the outer bark, the dark bands of the parenchyma right 
and left of the bundle are alternate in their arrangement rather than continuous. 
The “ orthenchymous ” disposition of the parenchymatous cells is sometimes seen in 
transverse sections, as in Plate XXVIII. fig. 30, h" ; but in these instances I have no 
doubt that the section has passed somewhat obliquely through the tissue in question. 
I shall call attention to some further peculiarities in this parenchymatous layer when 
describing the vascular bundles (m) which traverse it. 
The outermost layer of the bark (Plate XXIX. fig. 35, k) is also a well-defined one, 
which scarcely differs in its essential features from the prosenchymatous layer of 
Dictyoxylon Oldhamium. Its usual thickness is about ’021 ; but, as we shall immediately 
see, it is liable to undergo a sudden enlargement at special points. In the horizontal 
sections (Plate XXVIII. fig. 30, k, & Plate XXIX. fig. 35, k) it exhibits a radiating series 
of alternating bands of parenchyma and prosenchyma, the former being light-coloured 
and semitransparent, and the latter of a denser texture and a darker hue — conditions 
which are identical with those seen in the corresponding layer of I). Oldhamium 
(Plate XXIV. fig. 10). The prosenchymatous fibres have a diameter of about '0005, 
occasionally expanding to '001. 
In radial vertical sections (Plate XXIX. fig. 32 ,k", & Plate XXXI. fig. 45, k) the cells 
of this layer appear in the two forms of prosenchyma and of elongated parenchyma of the 
prismatic cylindrical variety with square ends. In tangential sections these tissues are 
arranged in the same way as in I). Oldhamium , viz. “the prosenchymatous bands form a 
network enclosing vertically elongated parenchymatous areolae of a lenticular form. But 
the plant under consideration differs from the Oldham one, so far as this portion of the 
bark is concerned : — 1st, in the greater relative thickness of the prosenchymatous bands; 
and, 2nd, in the smaller size and almost linear vertical form of the enclosed areolae. A 
innumerable modifications of parenchyma and frequently seen amongst living Cryptogams ; but if we do give it 
a special name it must be “ orthenchyma.” Mr. Linnet’s term involves an impossible, i. e. an ungrammatical, 
combination of noun and adjective; besides which mine is shorter, and accords better with its similar 
modifications of Bothrenchyma, Orthanthera, &c. 
