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XXI. Observations on the Structure of the Stem im certain Si the Natural Orders 
Caryophylleæ and Plumbagineæ. By DANIEL OLIVEX, Jun., F.L.S. 
- Read December 10th, 1858. 
CARYOPHYLLEÆ. 
THE internal structure of the stem in certain suffruticose species of the genus Acantho- 
phyllum presents some interesting anomalies which appear to me to be undescribed. I 
venture, therefore, to communicate to the Linnean Society this brief memorandum, as a 
further contribution to an already accumulated store of material in our possession relating 
to what we are accustomed to regard as abnormal modes of arrangement in the elements of 
Dicotyledonous wood, furnished to us by species often widely removed in the order of their 
natural affinities. The time may not be distant when a careful correlation of all our facts 
may be seasonable, and likely to render good service, not only to systematie botany, but 
also in enabling us to attain to a more comprehensive perception of vegetable structure 
generally. At the present time, how isolated, as well as fragmentary, are the items of 
our knowledge upon this subject ! 
The points of peculiarity in the species of Acanthophyllum to which I wish to direct 
attention at this time are—1st, the general relative arrangement of the vascular and cel- 
lular tissues or ‘systems’ of the stem; 2nd, the histological character of some of these 
tissues ; and 3rd, the occurrence in remarkable abundance, in some species, of frequently 
| large concretions of oxalate of lime in the parenchyma of the stem. To the difficult and 
time-absorbing study of the relations subsisting between the vascular bundles and the 
leaves, scapes, adventitious roots, or other axial appendages, I cannot at present address 
myself. Their connexion, so obscure and imperfectly understood even in succulent plants 
with lengthened internodes, is much complicated by a dense habit and dividing woody 
stem, apart from the difficulties attending the examination of specimens which have been 
dried many years. In regard, however, to this point, I may say that I am quite unable 
to attribute the differences in internal structure, presented by the different species, to a 
varied disposal of lateral organs; the mode of arrangement of the leaves is, upon the 
whole, very uniform in the plants which I have had through my hands. 
In this notice, I speak of the perennial, leaf-hearing, woody, and frequently branching 
axis of the genera Acanthophyllum, Arenaria, and Dianthus, as the stem: in the present 
terminology of these parts, there is, by the way, I think, somewhat ar a vagueness and 
laxity, which, without multiplying technicalities, or further burdening our glossaries, 
might be removed. : 
With regard to the arrangement of the tissues of the stem :—In some of the species of 
Acanthophyllum, as also in Dianthus and Arenaria, a manifest, though often very wise 
trie pith occurs ; in the first-named genus, however, often deranged, as are also the woody 
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