258 SIGILLARIEAE. 



have here to be brought into comparison, that of Gymnosperms on 

 the one hand and that of Lycopodiae and Lepidodendrae on the other, 

 would require a lengthy inquiry into the elementary anatomical ideas of 

 French and German authors. This would carry us too far from our im- 

 mediate subject, and the intimations already given will be sufficient for the 

 botanist. An inquiry into the comparative anatomy with special reference 

 to this point might possibly bear good fruit ; it might perhaps bring us nearer 

 to the understanding of the mode in which the existing types of structure 

 in stem and root have been developed from a common initial form. 



We cannot leave the consideration of the leaf-trace without a brief 

 notice of the two small lateral scars, which like a pair of brackets inclose the 

 place of fracture of the vascular bundle in Sigillariae, and which were 

 observed in similar form on the scar of Lepidodendrae. Renault l has shown 

 in the case of Sigillaria spinulosa that they are not remains of vascular 

 bundles, but are simply parenchymatous, and Stur's^ statement, who refers 

 them to the division of the foliar bundle in the cortex, must be corrected 

 accordingly. On other points Renault's account does not supply us with 

 much certain information with respect to these objects. He usually terms 

 them ' lacunes,' and says that they are gaps on the two sides of the vascular 

 bundle; in the preface 3 , which is directed against Williamson, he says: 

 1 the two lateral lacunae answer to gum-canals.' But the statement in the 

 same place 4 , that these canals pass through the entire thickness of the 

 rind, does not properly agree with his own drawings, in which they by no 

 means appear everywhere close to the vascular bundle ; they may possibly 

 have been at an unusual distance from it and could not be included in the 

 drawing. This will be seen by comparing his figures'* ; and other figures 6 , 

 in which they certainly appear, show them in such variety of form that it is 

 hopeless to think of forming a clear idea of their character. In any case we 

 cannot regard it as proved, that they represent or inclose gum-passages. 



Renault 7 gives some transverse sections of leaves of Sigillariae, which 

 show a single very broad diploxylous vascular bundle. It is quite possible 

 that these remains really belong to Sigillariae, but it is certainly not yet 

 proved, as Renault 8 himself admits when he says, 'which I think may be 

 referred to Sigillariae on account of their outward form,' &c. 



As regards the affinities of Sigillariae, now that the ideas of older 

 authors, who like Corda, for example, compared them with Cacteae and 

 Euphorbiae, have been definitively set aside, there remain only two opposing 

 views, one of which was founded by Brongniart and places them with 

 Cycadeae, while the other is maintained by Goldenberg, Schimper, and the 



1 Renault (8). a Slur ,5), p. 293. s Renault (2), vol. iii, p. 4. 4 Renault (2\ 



vol. iii, p. 5. * Renault (1), t. 12, f. i and 8, t. 3, f. 17, t. 5, f. 32. * Renault (8\ t. 3, f. 18, 

 t. 5, f. 31, t. 6, f. 33. T Renault (1\ t. 12, ff. 6-9. " Renault (V>, p. 265. 



