SIGILLARIEAE. 251 



angled in Sigillaria scutellata 1 , S. mamillaris 2 , and S. alveolaris 3 . S. 

 Knorrii, Brongn. also (see above on p. 245) and S. oculata 4 appear to 

 belong to this group. I also find them so arranged in several pieces 

 of Rhytidolepis in my collection. Lastly the scars appear from the 

 figures to be placed not in broad zones of the circumference of the stem, 

 but in single widely-separated circles, in Sigillaria Brardii and S. spinulosa 

 (see the figure cited above on p. 246), the only species of Clathraria and 

 Leiodermaria in which they are known. Renault 5 says that they must 

 have been arranged in these two species 'in a spiral with more or lesjs 

 distant turns ' ; I have never had the opportunity of seeing them myself. 



Authentic remains of Sigillariae with the structure preserved are 

 extremely rare. A single diminutive fragment of a small stem of Sigillaria 

 Menardi is all that is at present known from the group of Cancellatae. 

 This specimen was made use of by Brongniart 6 for his famous monograph, 

 and it was there described under the name of Sigillaria elegans, but Zeiller 7 

 has proved that this is a wrong determination and that it belongs to 

 S. Menardi. S. elegans does not generally occur in deposits so recent 

 as those which contain the siliceous fragments of Autun, from which this 

 specimen was obtained. The transverse section of it shows a broad 

 medullary tube, but the tissue has disappeared and been replaced by a 

 homogeneous mass of silica. The tube is immediately surrounded by a 

 ring of many crescent-shaped strands of tracheides, which have their con- 

 vexity turned inwards and are in lateral contact with one another, and in 

 which the narrowest elements are in the concavity of the outer side. 

 The strands appear to be entirely composed of scalariform tracheides- 

 of considerable length. The leaf-trace-bundles join them on their outer 

 side. This ring is surrounded by a mass of secondary wood which is 

 divided into separate wedges by primary medullary rays, and each wedge 

 corresponds to one of the inner bundles. This woody mass is of perfectly 

 normal character, and like the secondary wood of Cycadeae is divided by 

 fascicular rays into many narrow plates, in which the transverse sections of 

 the scalariform tracheides are arranged in regular radial rows. The leaf- 

 trace-strands run almost horizontally through the secondary wood, and it 

 is not till they reach the rind that they begin to ascend in steep curves. 

 The consequence is that they pass through the wedges of the wood very 

 nearly in the transverse direction, so that if the transverse section en- 

 counters one of them, the wedge of wood is seen to be divided by it into two 

 parts, as is shown in Fig. 28 and in Brongniart's 8 and Renault's 9 figures. 

 Little of the cortical tissue is preserved in our specimen ; the inner and 



1 Zeiller (1), t. 173, f. i. 3 Lesquereux (1), vols. i, ii, t. 72, f. 5. 3 Goldenberg (1), 



t. 7, f. 16. * Geinitz (1), t. 5, f. 10. 5 Renault (2), vol. iii, p. 9. Brongniart (7). 



7 Zeiller (12), p. 259. 8 Brongniart (7), t. 25. 9 Renault (1), t. n, f. 13. 



