88 
ORGANOGRAPHY. 
BOOK I. 
It seldom happens that any part of the vascular system 
intermixes with the pith, which is usually composed of cellular 
tissue exclusively ; but in Ferula and the Marvel of Peru, it 
has been proved by Mirbel and De Candolle, that bundles 
of woody fibre are intermixed; in Nepenthes there is a con- 
siderable quantity of spiral vessels scattered among the cel- 
lular tissue of the same part; and many other cases of a 
similar kind are now known. In Nyctaginaceae generally, 
in Piperaceac, Cycadaceae, Chloranthaceae, &c., this occurs, 
and has been made by Professor Schultz the character of a 
large division in his Natural System of Botany, called by 
him Synorgana dichorganoidea ; but such cases may be found 
in Loranthus, and are not uniform in the orders quoted: in 
Boerhaavia repanda, for example, the pith contains no bundles 
of vascular tissue, but is filled ivith Jistulce containing very soft, 
lax, spheroidal, cellular tissue, surrounded hy smaller, harder, 
and more cubical tissue, which passes into the medullary rays ; a 
most curious organisation. 
The Bark is the coating of the stem immediately above 
the wood, to which it forms a sort of sheath, and from which 
it is separable without difficulty at certain seasons. But, 
although it appears as an independent formation, it is, in 
reality, organically connected with the wood by the processes 
of cellular tissue, which, under the name of medullary rays, 
pass through the wood, and lose themselves in the thickness 
of the bark. Formerly bark was distinguished into cortical 
or cellular integument, under whi(jh name was comprehended 
the whole of the external parenchymatous part, and liber or 
inner bark, a name used to denominate the fibrous woody 
portion lying next the alburnum. But it is necessary to look 
at the organisation of the bark with more precision, if we are 
to understand all the peculiarities found in its many modi- 
fications. It appears to me that the observations of Mold are 
the best and most complete which have hitherto been made 
upon this very important subject : they, and many more of 
considerable value, by Dutrochet, Link, and others, rentier 
a peculiar nomenclature for the parts of the bark indis- 
pensable ; so many false or indefinite ideas are there which 
attach to the older terms. Bark may be described anato- 
