CALAMODENDRON. 23 



Fig. 5 exhibits a longitudinal section of the same stem, magnified fifty diameters. 

 With this magnifying power the walls of the tubes give evidence of oval openings, placed 

 horizontally ; but they are scarcely so well defined as those in the large specimen No. 1 ; 

 and the walls appear to be slighter (even after allowing for the smaller size of the speci- 

 men), than those in the specimen first described (p. 20). 



The two sections last mentioned, more especially the longitudinal one, are obscured 

 in parts by patches of coaly matter ; and, as we should expect from the appearance of the 

 transverse section of the stem, we find that a portion of the central axis has been destroyed, 

 and no trace of its original structure left. The coaly matter is, no doubt, owing to the 

 line of section being taken close to the bark, which is generally found converted into 

 bright coal. 



§ 3. The Specimen {Calamodendron commune) No. 4. 

 (Plate III, fig. 7.) 



Plate III, fig. 7, shows a very small specimen of Calamodendron, magnified thirty-four 

 diameters, with the central axis (or pith) in a complete state of preservation. The 

 diameter at the broadest is only j^gth of an inch. The stem, no doubt, was originally 

 cylindrical, like those of all other specimens of this genus of plants ; but it has assumed 

 an oval form from pressure when it was in a soft state. The central axis, or pith, is 

 composed of large pentagonal utricles (some filled Avith a black colouring matter), arranged 

 without order, except that the largest in size is found near the centre. The woody 

 cylinder surrounding the central axis consists of nine wedge-shaped masses of pseudo- 

 vascular structure, radiating from as many orifices, and similar in all respects to that of 

 the two larger specimens, Nos. 1 and 3, previously described (pp. 20 and 22). Indeed it 

 appears to be an individual of the same species, in a younger stage of growth. 



The form of the utricles composing the central axis somewhat resembles that found 

 in small specimens of Sigillaria vascularis. In all my longitudinal sections of this small 

 stem, I have not been able to satisfy myself that they are marked on their sides by fine 

 horizontal striae ; but still they appear to be different from ordinary cellular tissue, 

 and have more the form of utricles than of cells. This is a very material point to clear 

 up, and probably the examination of other specimens may enable us to elucidate it 

 more satisfactorily. 



■^ 4. The Specimen (Cone of Calamodendron commune^ No. 5. 



(Plate IV, fig. 1.) 



The fructification of Calamites was long ago supposed by Ettingshausen and others 

 to be the same as Volkmannia ; and the great number of small cones, evidently nearly 



