508 Scientific Proceedings, Royal Dublin Society. 



Silurian land-plants of ascertainable characters normally enter into the earliest 

 flora. It is not inconceivable that the Devonian beds are pre-eminently rich 

 in Bothrodendron, because this genus has in them reached its maximum 

 development, having begun in the earlier Silurian epoch. It is known to 

 be waningly represented by several species in the Middle, and by only 

 one species — B. sjmrsifoUmn — in the Upper Coal Measures. 



Calamitoid Charactevs, 



There is one interesting feature observable in the impressions of older 

 stems, especially of Bothrodendron IdUorkense, -which deserves more tlian passing 

 notice. This feature is illustrated in the photographs (Plate XXXVIII, figs. 

 1-4). Pig. 2 represents a piece of stem 80 cm. long and 10 cm. broad, which, 

 at first glance, might be mistaken for a Calamite. It is not simply that the 

 surface of tlie stem possesses a longitudinally striate epidermis ; the stem is 

 strongly fluted or grooved (fig. 3), revealing a marked structural feature. In 

 some small pieces of stem (Plate XXXV, figs. 4 and 5) evidently stripped of the 

 cortex the ridging is so pronounced and Equisetaceous that I felt sure, until I 

 noticed the distant leaf-scars in the Knorria-stage, tliat the specimens were 

 part of the Calamite. Heer's figure (Tf. x, fig. 8 : Flora d. Baren-Insel) of 

 the young stem of his Calamites radiatus is evidently made from a specimen 

 in the same stage and state as this Kiltorcan material. The illustration (Plate 

 XXXVIII, fig. 8), which represents a small piece of Plate XXXVIII, fig. 2 

 enlarged, shows, in addition to the continuous straight vertical grooving, a 

 transverse zonation which corresponds in position with the leaf-scars when 

 these occur in horizontal whorls, and suggests the presence of nodal diaphragms 

 (Plate XXXVIII, fig. 5). The magnificatiou of the fluted surface shows tliat 

 the leaf-scars occur independently of tlie vertical ridges, sometimes on the 

 ridges, at other places in the grooves between them. The flutiug is observable 

 in flattened stems 12 inches wide, with typical leaf-sears still clearly recogniz- 

 able on the epidermal surface of the stem — a sign apparently, as in Lepido- 

 dendron, of absence of periderm, owing to the adaptation of the epidermis to 

 the increase in girth of the stem. It is to be seen, too, along with transverse 

 zonation in comparatively young stems, 1 cm. wide, apparently in certain 

 conditions of preservation, e.g. in the stem figured (Plate XXXV, fig. 3) in 

 which the leaf-scars are still close together. A striking difference is observable 

 in this stem in the arrangement of the leaf-scars. Those on the right-hand 

 side are arranged in a zone-like manner ; and this part of the stem is 

 transversely ridged or zoned. On the left-hand side the leaf-scars are less 

 zonately arranged, wider apart, and appear to be assuming the quin- 

 cuncial position. Running down the centre of the impression is a faint 



