CALAMODENDRON. 



19 



The form of the sporangium, when it is of large size, and had attained a state of 

 maturity, is generally of an irregular egg-shape, as before stated ; but, in some small 

 specimens, it has a cordate or pear-shape form in tangential sections, and is filled full of 

 dark-coloured spores ; and its external cover, composed of a single row of cells, is thicker 

 and more substantial. This envelope appears to have expanded and become thinner as it 

 grew older ; and, at length, when the spores were ripe, it probably burst and dispersed 

 them. Specimens of sporangia are to be found in all stages of their growth ; but the 

 cones, although generally showing most beautiful structure, have been very much dis- 

 arranged, and it is extremely difficult to get true sections of them, especially in a longi- 

 tudinal direction, parallel to their central axis. A great number of specimens had to be 

 examined before the quadrate arrangement of the sporangia, as first shown by Ludwig, 

 could be made out, as well as the occurrence of six processes or spindles in the stead of 

 that author's five, and the twenty-four sporangia against his twenty. 



III. Description or the Specimens. 



^ 1. The Specimens [Calamodendron commune) Nos. 1 and 2. 

 (No. 1, Plate I, fig. 1 ; Plate II, figs. 1— G. No. 2, Plate I, fig. 2.) 



Specimen No. 1 (Plate I, fig. 1) is about eight inches in length, and ten inches in 

 circumference. Although no doubt originally cylindrical, it is now of an irregular 

 pear-shape from the pressure to which it was probably subjected in the process of minera- 

 hzation. The outside of the fossil, which is in a decorticated state, is marked by fine 

 longitudinal striae ; but it does not show the ribs and furrows so commonly found on 

 what is generally termed the outside of Calumites, nor are there any joints or nodes 

 apparent on it. There is some evidence of the outer bark in a thin coating of bright coal, 

 the specimen having shelled out of the matrix in which it was imbedded, and left its 

 bark in the stone. But in another specimen (No. 2 ; Plate I, fig. 2), from the same 

 place as No. 1 came, we have an example of a Calamodendron which has been split 

 through the middle, and which there shows, on the outside of the central axis, the usual 

 ribs and furrows so long considered as belonging to the outside of the plant ; and in an 

 upper portion of the specimen, not shown in the Plate, is a joint. 



On looking at a transverse section of No. 1 (Plate II, fig. 1), the wedge-shaped 

 bundles of pseudo-vascular structure are seen squeezed together, and divided by other 

 wedge-like masses of coarse cellular tissue, of a lighter colour ; but there is no trace left 

 of the central axis (or pith) of the plant. This, as has been previously stated, is nearly 

 always the case with large specimens, so far as my experience goes. In the specimen 

 now under consideration, owing to the position of its fracture, we cannot obtain any 



