FERNS— INCEETJE SEDIS— BRITTSIA. 99 



plant may be gained from an inspection of the forms shown in PL XL VII, 

 Fig. 3, and PL XLVIII, Figs. 1 and 3. All of the pinnae are of the same 

 type and agree in the expansion of the flat axis above the base in the 

 middle portion of the pinna, the surface being marked by coarse, irregular 

 strise corresponding to the vascular bundles which are spread out in broad, 

 lax, sinuate bands in the lateral pinnae. The marginal lamina of the main 

 axis is continuous with that of the lateral rachises, forming lingulate expan- 

 sions about the latter. A marked feature in the lateral pinnae., however, is 

 the position of the pinnules in a different plane from the lamina. The 

 pinnules originate, apparently with much constricted bases, at alternating 

 points on the lamina close to the rachis, the roundish, pitlike vascular cica- 

 trices, when the pinnules are fallen or removed, giving the general effect of 

 sori or sporangia on the lamina. This character is seen in Fig. 3, PL XLVII, 

 or Fig. 3 on PL XLVIII, in which, as in most of the specimens, the pinnules 

 are wholly removed and only the inarginal lamina is left. It is difficult to 

 determine whether these pits marking the passage of the vascular bundles 

 to the pinnules are actually within the margin of this rachial lamina or not. 

 In a number of cases the broad expanse of the lamina seems continuous 

 around the cicatrice, as though the pinnule emerged from its surface. Nev- 

 ertheless, it is quite possible, and would be more natural, for the pinnules 

 to spring from very deep sinuses on the lamina, whose greatly dilated broad 

 expansions on the same side overlap so compactly ^s to have every appear- 

 ance of a continuous limb. These expansions, one of which is shown in Fig-. 

 4, PL XLVII, not only lie in the approximate plane of the racliis, but they 

 may clearly be traced distinctly separate from the pinnules opposite them; 

 and, although the margins are g-enerally obscure and apparently erose or 

 crenulate. the attachment of the piimules is evidently quite narrow. 



The pinnules themselves are borne in two rows on each of the lateral 

 pinnae. From the point of attachment, marked by the cicatricial pits in the 

 depinnuled pinnae, they curve outward slightly, then inward so that those 

 on one side of the rachis overlap those on the other side, alternately imbri- 

 cating, the combined expanse of both rows being much greater than the 

 rachial lamina. In Fig. 1, PL XLVIII, is shown the greater part of a frond (?) 

 in the lower left of which the pinnules are still in place, as is better illus- 

 trated in Fig. la. Fig. 2, the photographic enlargement, 2a, and the details, 

 Fig. 26, show the double series of broken pinnules still in their normal 



