XV. 



REMAINS OF STEMS OF DOUBTFUL AFFINITY, IN WHICH 

 THE CHARACTER OF THE SURFACE IS UNKNOWN. 



WE have still to examine a certain number of fossil stems, the position 

 of which is open to question because the character of their surface is quite 

 unknown. All stems of this kind, which could be connected with definite 

 groups of plants, have been discussed in the preceding chapters ; here 

 therefore we have to deal only with a few forms, for which no appropriate 

 place could be found before. 



The first that may be mentioned is the genus Sigillariopsis, Ren. 1 , 

 which might perhaps have been noticed in the chapter on Sigillariae. Its 

 author has obtained several specimens from the pebbles of Autun. The 

 one which he has figured 2 consists of a fragment of stem in rather im- 

 perfect preservation, which is surrounded by the spirally arranged leaves 

 still in their natural position. The transverse section of the stem, small 

 in diameter and with the rind and pith badly preserved, shows like 

 Sigillaria Menardi a narrow layer of secondary wood with scalariform 

 tracheides on the inside and pitted tracheides on the outside, after the 

 manner of Cycadeae. The longitudinal section 3 in the same work should 

 also be compared. Inside this ring of wood are numerous primary wood- 

 strands, as in Sigillaria, lying close together, which, as we are expressly 

 told, are in a bad state of preservation, but which have their spiral 

 tracheides outside, as in that genus, and next to these on the inside 

 scalariform and pitted elements. We see that all this agrees perfectly 

 with what is known in the case of Sigillaria Menardi, with the single 

 exception of the pitted tracheides which are not found in that species. 

 The leaves too are similar, narrow-lanceolate or linear, as may be con- 

 cluded from their rhombic or somewhat irregularly triangular transverse 

 sections ; but the rhombic sections show two vascular bundles close to 

 one another, while in the triangular section which is figured there is 

 only a median bundle. Renault considers that the latter is the transverse 

 section of the tip of a leaf, and says 4 : 'In the broadest part of the leaf 

 are seen two vascular bundles, which are reduced to a single bundle 



1 Renault (1), p. 270. 2 Renault (1), t. 12, f. 15. s Renault (1), t. 12, f. 17. 



4 Renault (1), p. 271. 



A a 2 



