MR. HENFREY ON THE ANATOMY OF THE STEM OF VICTORIA REGIA. 29 1 
eye, which seems to be analogous to the layer of ‘ cortical substance ’ occurring in 
considerable thickness in the rhizomes of certain aquatic Monocotyledons, such as 
Sparganium, Typha, See., and less extensively in all herbaceous plants of that class. 
This layer sends out broad flat laminae which are directed both horizontally and 
vertically into the spongy substance, which they thus subdivide into compartments 
and greatly support and strengthen (Plate XIX. fig. 2 f; Plate XX. figs. 3,4f). As 
the firm walls of the cavernous spongy layer are of the same character and continuous 
with the white cortical layer, perhaps it would be most correct to consider the spongy 
substance as part of that layer, hollowed out by air-cavities to lighten the structure. 
In those Monocotyledons, which, like Sparganium, have a broad cortical layer, 
there usually exists a firm ‘ fibrous layer,’ composed of ducts consisting of the inter- 
lacing ends of the vascular bundles of the stem, which layer gives origin to the vas- 
cular bundles of the roots, and also forms the boundary between the ‘ cortical sub- 
stance’ and the vascular central mass, representing the wood in these plants. I 
could not detect a fibrous layer of this kind here, and perhaps its absence stands in 
some relation to the peculiar arrangement of the roots, for in the plants where it 
occurs, adventitious roots are given off in all parts of the stem, driving their vascular 
bundles from the fibrous layer everywhere present. In Victoria the roots occur 
only at the bases of the petioles, and they are there supplied by vascular bundles 
sent out expressly for them. 
The central substance of the stem presents at first sight a confused mass of inter- 
lacing fibres imbedded in cellular tissue, which here exhibits no sign of division into 
regions corresponding to pith or medullary rays, Plate XIX. fig, 2g; Plate XX. 
figs, 3, 4, 5 g. The character is quite Monocotyledonous, except that there is evidently 
frequent anastomosis of the interwoven fibres, which is not commonly found in the 
Monocotyledons. The outer part of this vascular region contains fibres of smaller 
diameter than those of the centre, many of which run horizontally round the stem 
(Plate XX. fig. 3) ; more internally, the fibres mostly run obliquely and sometimes 
transversely through the stem (Plate XX. fig, 4), and in the inner parts some of the 
fibres are nearly vertical, Plate XX. fig. 5. When examined by the naked eye the fibres 
appear opake, and are surrounded by a semi-transparent layer, which again is sur- 
rounded by the opake cellular parenchyma of this central layer ; portions of the cel- 
lular tissue, near the outer part of this region, also present this semi-transparent 
appearance, which is caused by the absence of air-cavities in the tissue ; the vessels 
containing air, and the general parenchyma, which is freely supplied with air-cavities, 
as in most water plants, appear opake under water, from the reflexion of light which 
the contained air causes. 
At the place where each leaf and bundle of roots is borne, a branch-like process of 
the central vascular mass is given off (Plate XIX. fig. 2 a, b), in which run horizontally 
the vascular bundles for the leaf {a) and roots {b). Those for the former appear to 
be mostly derived from the central part of the vascular mass (Plate XX. fig. 4 a), those 
