CALAMODENDRON. 21 



the marked difference of being composed of cells and not of barred vessels, as is the case 

 in that plant. 



The origin of the pseudo-vascular wedges is from the oval orifices, and they seem to have 

 no apparent connection, so far as my observation goes, with the central axis or pith. In 

 small specimens the number of these orifices had been noticed as far as six ; whilst in the 

 large specimen now under description, as previously stated, they amount to seventy-five in 

 number. Specimens of these wedge-shaped masses, similar in structure and external 

 character to those of No. 1, can be seen of different sizes from some so small as to consist 

 of only three tubes in breadth (from the orifice to the outside) up to larger ones, with 

 more than one hundred tubes. 



The specimen shows what at first sight might be mistaken for annular rings, or depo- 

 sitions of successive growth ; but when carefully examining it under the microscope, we 

 do not find in it sufficient evidence to estabhsh. with certainty any appearance of the 

 cessation of growth, like that shown by the annular rings of an exogenous plant of the 

 present day. Other specimens in my cabinet give more evidence of successive growths; 

 but still in my opinion scarcely sufficient to establish the former existence of distinct 

 annular rings, showing the stoppage of growth, like that which now takes place in our 

 hard- wooded exogenous trees ; and these appearances in the specimen may have been 

 caused, at the time of the mineralisation of the specimen, by successive deposits of 

 mineral matter. However they may have been produced, these rings appear to me to 

 be nearly similar in Calamodendron to those usually seen in transverse sections of the 

 external woody cylinder of Si^illaria, as well as those in the outsides of Dadoxi/lon. 



The tangential section Plate II, fig. 5, is taken near the commencement of the pseudo- 

 vascular bundles, and show^s them of small size and divided by broad spaces of coarse 

 cellular tissue. That of Plate II, fig. 6, is taken nearer to the circumference, and shows 

 the pseudo-vascular bundles separated by others of coarse cellular tissue, elongated oval in 

 section. Neither of these sections, however, exhibits the oval-shaped bundles of vessels 

 proceeding from the joints, and communicating with the branches. These will be shown 

 in other specimens, hereinafter described. 



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

 (Plate III, figs. 1—6.) 



This is of small size when compared with Nos. 1 and 2 last described, and is ex- 

 hibited in Plate III, fig. 1, displaying only one side and the top of the specimen. It is 

 one inch in length, and three-tenths of an inch in diameter across its major axis. The 

 outer bark has been converted into a film of bright coal, which adheres to the stony 

 matrix, and thus leaves the outside of the stem in a decorticated state. This stem, unlike 



