522 



FILICALES 



As a further Example Hawlea ^ may be mentioned, which is also of 

 very early occurrence. Here the sorus is of the circular form, as before : 



the sporangia are sessile and 

 elongated-ovoid in form, and radi- 

 ate outwards from the centre of 

 attachment, so that the slit of 

 dehiscence on the inner side is 

 directed upwards, and the spor- 

 angium when open has the form 

 of a boat (Fig. 289 B). Stur de- 

 scribes a rudimentary apical annulus 

 in these sporangia, but it is not 

 clearly shown in his figures. The 

 sorus of Hcrivlea appears most 

 nearly comparable to that of the 

 modern Angiopteris, but this com- 

 parison would be accepted with 

 greater confidence if the micro- 

 scopic details were better known 

 by a study of sections. 



Lastly, under the name of 

 Danaeites certain Ferns have been 

 described, which, so far as can be 

 judged from the study of im- 

 pressions, conform to the Danctca 

 type of sorus (Fig. 290). It may 

 be a question whether the rela- 

 tion of the sporangia together, and 

 the mode of their dehiscence were 

 exactly as in the modern Danaea, 

 but at least the plants appear to 

 have been Marattiaceous, and to 

 have had elongated sori. They 

 come from the Coal Measures, 

 Keuper, and Lias. 



Having regard to the fact that 

 the comparisons above sketched 

 do not relate to one or two, but 

 to several different genera, it 

 appears that there is ample evi- 

 dence of the early existence of the 

 Marattiaceous type. It would in fact be difficult to find clearer evidence 

 of affinity between a recent and a fossil group of plants, while, as we shall 



'Mr. Kidston suggests in me that Asterotheca is really identical with ffau'/ca, i In- 

 apparent difference being due to conditions of preservation. 



FIG. 289. 



Fructifications from the carboniferous formation. 

 A = Senftenbergia ophidermatica : to the right the posi- 

 tion of the sporangia on both sides of the median netve 

 of the pinnule : to the left a single sporangium, seen 

 from above. B = Haiulea Mittonl : to the right a pinna 

 with the sori on the extremities of the lateral nerves : to 

 the left a single sorus more highly magnified. C 

 Oligocarpia liinisatiiiii's, showing position of the few- 

 membered circular sori on the nerves of the pinnule. 

 D^Scolecopteris polymorpha, Hrongn : to the left a 

 pinnule showing the position of the sori in transverse 

 section : to the right a longitudinal section of a sorus 

 in which the sporangia are united below into a columnar 

 receptacle. E = Astcrotheca sternbergii : to the left the 

 pinnule with sori: to the right a side view of a sums 

 and a sorus in radial section. /) and E diagram- 

 matically represented. (All Figures after Stur. From 

 Solms-Laubach's Fossil Botany.) 



