482 
PEOFESSOE HEXFEEY OX THE AYATOIMT OE AHCTOELi EEGLl. 
auction of annual rings takes place. On the other hand, we know of no case of its 
occurrence in Monocotyledons. But although the ‘ scattered’ anungement is so rare in 
Dicotyledonous steins, instances of it do actually occui- and one case recently made 
known by M. Vaupell* is especially interesting, as it radicates that we must be xen 
cautious in regarding it as a systematic character. In_ the rhizomes of the genus 
Primula the fihro-vascular bundles usually stand in a cu'cle around t e pit , as ra 
P mlqaris, sinensis, and others; but in P. Auricula the bundles are scattered generaUy 
through the parenchymatous structure without any appearance of a distraction between 
pith and wood, essentially therefore, although in a more simple form, exhibiting the 
same aberration as Victoria. The existence of this character in certain species only of 
a clearly-marked genus would be fatal to its use as a systematic character, ^d we not 
know that no single character in natural classification can be regarded as absolute , . li, 
however, its importance be admitted, it becomes necessaiT to raquii-e how far* it is to be 
allowed to prevail, and what attending circumstances must be looked to ra estimatmg it 
In the present case, when we pass from the arrangement of the fibrowascidar bundles 
to the structure of the bundles themselves, a most important qualiBing cmciimstance 
becomes evident. The horizontal and perpendicular sections given with my former 
memoir + show that the fibro-vascular bundles consist of a central group of spmal vessels 
surrounded by delicate elongated cells, forming a kind of cambium tissue: there is no 
wood here, nor anything comparable to the so-called liber-fibres of the bundles of ordi- 
nary Monocotyledons. The vascular bundles are reduced to them simplest elements.- 
a few vessels enclosed by a cambium region. In this state they agree with the rudi- 
mentary condition of the Dicotyledonous vascular bundle, which is especiaUy charactei- 
ized by its peripheral region being composed of cambium, givrag it the power of grout i, 
while in the bundles of Monocotyledons the cambium tissue is, as a rule, found ra the 
middle part, with the older woody structure external to it, forming a fixed boundary, pre- 
cluding further growth. ^ 
Considering the rudimentary condition of the vascular bundles of the stem, we should 
perhaps be rash in drawing any positive conclusion from them structure; yet the 
evidence, such as it is, derivable from this is in favour of the reference of 1 ictoria to 
Dicotyledons. i i i r 
A far more decided indication in the same dmectioii is afforded by the plan ol 
arrangement of the vascular structures in the roots. The typical structure of the lOot 
of a Monocotyledon is that of a cylinder of parenchymatous tissue contammg a centra^ 
woody axis, which axis, when cut across, exhibits a centre composed of more oi less 
* Untersuch. iiber das periplier. Waclistlium d. Gefassbdl. der Dicotyled. Ebizome ; Leipsic, 1855. ^ 
t The so-called ‘anomalous’ stems of Nyctaginaceje, Clienopodiacese, Meuispermaceffi, &c., present coii 
ditions which greatly increase the difficulty of laying down a typical character for the stems of Dicotjdedons ; 
but researches at present in progress on these structm’es do not lead to our regarding them as rea y m ei- 
mediate between the Dicotyledonous and Monocotyledonous. 
J Philosophical Transactions, 18o2, Plate AX. figs. 10 and 13. 
