PEOFESSOE HEXFEET OX THE AXATOMY OF TICTOEIA EEOIA. 
481 
necessarily incapable of a development similar to that of the cambium region just referred 
to, inasmuch as they are closed in all round by the other perfectly-formed elements of 
the fibro-rnscular bmidle. 
The lower extremities of the bundles of Monocotyledons, moreover, do not anasto- 
mose collaterally below in the inner part of the stem, as those of Dicotyledons do ; 
they run more or less obliquely outwards until they reach the region where the central 
substance of the stem joins the rind, at vrhich point they usually branch and anasto- 
mose with their fellows above, below, and around, sometimes forming an intricate fibro- 
vascular plexus. The cellular tissue in the -sicinity of this region, forming the dmsion 
between the rmd and the medullary substance, partakes in some measure of the charac- 
ters of the cambium region formed by the collective bundles of a Dicotyledonous stem, 
since it is here that adventitious roots first arise ; and here also are produced those 
peculiar fibrous layers of increase which give so anomalous a character to the stems of 
Yucca, Dracaena, &c. But it must be observed that there exists this essential difierence, 
that the cambium layer is the outer, horizontally developed region (or outer side) of the 
Dicotyledonous bundle, Avhile this pseudo-cambium region of Monocotyledons is con- 
nected only with the inferior extremities of the closed fibro-vascular bundles. 
Applying these considerations to the structure presented by the stem of Victoria, we find 
unmistakeable resemblance to the typical structure of Monocotyledons in the arrange- 
ment of its bundles, and the entire absence of that kind of regularity which produces an 
annular appearance of the fibro-vascular structure in a cross section ; the great number and 
the isolation of the bundles, and the absence of a central medullary region are especially 
Monocotyledonous ; and the relative position of the bundles in their course is closely 
in agreement. The chief difierence consists in the collection of the bundles together 
into a kind of cord where they run out from the central region into the petiole — which 
arises from the comparatively narrow base of the leaf at its origin in the 'punctum vege- 
tationis , — and in the existence of numerous bundles connected with the roots running 
up and down and around the stem in the region immediately within the rind. The 
foimer of these points indicates an agreement with the Dicotyledonous type ; the latter 
departs less from the Monocotyledonous type than from the Dicotyledonous. 
The general agreement of structure with that typical in Monocotyledons may be 
admitted A^fithout our assuming that this should largely infiuence us in determining the 
systematic position of the plant it occurs in. The general resemblance of the leaves of 
Monocotyledons with dictyogenous venation to those of Dicotyledons, is an example of 
strongly marked Monocotyledonous plants exhibiting a resemblance in certain charac- 
ters to Dicotyledons. The weight attributable to such cases can only be estimated after 
a careful examination of the various modifications they present, and of collateral cir- 
cumstances. 
At first sight the annular arrangement of the fibro-v ascular bundles around a central 
pith appears a very important systematic character, since it is extremely rare to miss it, 
even in the most irregularly developed rhizomes of Dicotyledons, where little or no pro- 
