184 



D. H. Scott. 



Two fructifications, which will now fall under Pfendotheca, are 

 figured in my Studies in Fossil Botany, Figs. 94 and 95. The latter 

 represents a form of frequent occurrence, often exquisitely preserved, 

 which I propose to name Pieridotheca WiUiamsoni, as it was first de- 

 tected, though not described, by the late Prof. W. C. Williamson. 

 The sporangia are borne in sori on the segments of a much-divided leaf, 

 apparently of Sphenopteroid form. The pinnules are much incurved 

 and the sporangia are inserted on Uieir margins.^) The fertile lamina 

 is well-developed, and appears not to have undergone reduction. The 

 sporangia are sessile, with a multicellular base, and ellipsoidal or 

 nearly spherical in form, though their sides are often flattened by 



Fig-. 14. Fteridoflicca WiUiamsoni. Two sporangia, to show the annuli. From a 

 photograph by Mr. Boodle. X about 70. 



mutual pressure. The wall, as preserved, is usually one cell thick 

 and is provided with a conspicuous annulus, extending partly 

 round the sporangium, and, when cut lenghtways. strongly recalling 

 the familiar Polypodiaceous annulus (Fig. 14). Transverse sections, 

 however, show that the annulus is really two cells in width. The 

 spores, often well preserved, are numerous, and of one kind only, so 

 far as observed. There is clearly a strong presumption that Pterido- 

 tJieca WiUkimsoni was the fructification of a Fern. There is nothing 

 to connect it specially with the Botryopterideae, beyond the fact that 

 the annulus is more than one cell wide. This was perhaps a general 

 character of the annulate Fern-sporangia of Palaeozoic age; at least 

 no clear case of a uniseriate annulus has yet been demonstrated. 

 Though the pinnules are often beautifully preserved, we have no 

 further evidence as to the structure of the plant. 



^) Further investigation has convinced me that the body marked r in the 

 figure cited ("Studies", Fig. 95) is not a receptacle, but merely part of the incurved 

 pinnule. 



