246 SIGILLARIEAE. 



this kind (S. spinulosa) we owe to Germar 1 . The Leiodermariae bear 

 much the same relation to the preceding forms as Bothrodendrae bear 

 to Lepidodendrae ; they are separated from them on the whole in time 

 also, being chiefly found in the most recent formations that contain any 

 Sigillarieae, though Goldenberg has obtained a few of them, but rarely, 

 from the beds at Saarbriicken. In the specimen of Sigillaria spinulosa 

 figured by Germar the entire surface is rough with small anastomosing 

 folds ; its leaf-scars show the characteristic trace in the normal manner. 

 Close under the upper margin of the trace lies the ligular pit as a minute 

 point, and beneath each pit are other marks, in which the depressed centre 

 is surrounded by a circular wall. Ordinarily there are two of these marks 

 standing right and left of the median plane ; sometimes only one mark is 

 present in a lateral position, and occasionally there are none. They occupy 

 exactly the positions of the two marks in Lepidodendron, and are therefore 

 compared with them by Stur, though nothing of the kind is known in 

 other Sigillarieae. Germar had regarded them as the points of attachment 

 of prickles. Zeiller 2 and Renault 3 consider them to be the scars of 

 adventitious roots. Renault gives a figure of Sigillaria spinulosa 4 in 

 which they are distributed in groups, and do not occupy the regular 

 position, as in Germar' s specimen. Further investigation is desirable, but 

 I have not the necessary material. Whether Semapteris carinthiaca 5 

 from the anthracites of Carinthia belongs to Leiodermariae I cannot 

 positively say from the figure only. The cushions on the smooth surface 

 of the stem are far apart from one another and are somewhat decurrent ; 

 their scars certainly are like those of Sigillaria. . Semapteris tessellata, 

 also described in Unger' s work, may be a badly-preserved form of Clathra- 

 riae. Unger indeed would place not only these two forms but all the 

 Clathrariae as well with Ferns ; of Leiodermariae he does not speak with 

 perfect distinctness. 



Hitherto we have been speaking only of the surface-impressions. In 

 a cast these can be examined only, as was said above, when the whole of 

 the rind of coal is preserved. If this is removed, there remains behind an 

 inner impressed surface answering to some extent to the casts of Lepido- 

 dendrae, which are beset with linear bundle-traces. The surface of this 

 impression is quite smooth in Leiodermariae, but the vertical ridges are 

 plainly seen upon it in Rhytidolepis. But the leaf-trace is marked in both 

 cases by three protuberances, not by one as in Lepidodendrae ; the small 

 middle one it is true is often very indistinct, while the two lateral ones 

 appear plainly as parallel strokes. In those Rhytidolepis-forms which 

 have very broad ribs and narrow leaf-scars, such as Sigillaria reniformis 6 



1 Germar (1), t. 25, ff. i, 2. " eiller (3), p. 138. a Renault (2), vol. i. 4 Renault 



(2), vol. i, t. 17, f. 2. 5 Unger (10), t. 3, f. i. Brongniart (1), voL i, t. 142. 



