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XXI. Observations on the Structure of the Stem in certain Species of the Natural Orders 

 Cax-yophyllese and Plumbaginefe. By Daniel Oliver, Jun., F.L.S. 



B«ad December 10th, I8r>8. 



Cartophylleje. 



1 HE internal structure of the stem in certain suffruticose species of the genus Acantho- 

 phyllnm 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 aiiinities. The time may not be distant when a careful correlation of aU our facts 

 may be seasonable, and likely to render good service, not only to systematic 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 Acanthophylluni 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-bearing, woody, and frequently brandling 

 axis of the genera Acanthophylluni, Arenaria, and Dianthus, as the stem : in the present 

 terminology of these parts, there is, by the way, I think, somewhat of a vagueness and 

 laxity, Avhich, \rithout multiplying technicalities, or further burdening om- glossaries, 

 might be removed. 



With regard to the arrangement of the tissues of the stem : — In some of the species of 

 Acaiithophyllum, as also in Dianthtis and Arenaria, a manifest, though often very excen- 

 tric pith occurs ; in the fii'st-named genus, however, often deranged, as are also the woody 



vol. XXII. i; 2 Q 



