FILICALES 



primitive. It will be seen that this species has a stelar structure of the axis 

 of a type which also indicates its relatively primitive character in the genus. 

 The sorus of Oligocarpia from the upper Carboniferous corresponds 

 in its arrangement to that of Gleichenia (Fig. 312). O. Gutbieri and 

 Hndsaeoid.es show uniseriate sori with varying number of the sporangia, 

 as in G. flabellata ; but O, Brongniartii has accessory sporangia occupying 



FIG. 312. 



I. Oligocarpia Brongniartii, Stur. A =a sterile ; Z?=a fertile pinnule (y) ; C = a sorus 

 more strongly magnified. (After Stur.) 1 1. = two sori of the same species. Xss- (After 

 Zeiller.) III. Oligocarpia Giitbieri, Gopp. .4 = position of the sori on a segment of 

 the last order. XSQ. B = a sorus. X6o. (After Stur.) IV. ^Oligocarpia lindsaeoides 

 (Ett.), Stur. -4 = position of the sori on a segment of the last order. X3O. = a sorus. 

 Ca. sporangium. x6o. (After Stur, from Potonie's Lehrbuch.) 



the centre of the sorus, as in G. dichotoma. There is, however, a difference 

 of opinion as to the annulus, and it is upon this that the ultimate deter- 

 mination must rest : Zeiller recognises an annulus similar to that of the 

 Gleicheniaceae; but Solms Laubach * does not assent to this, asserting 

 that the supposed annulus is due to an effect of lighting of the specimen 

 under observation. Zeiller nevertheless adheres to his opinion. 2 Whatever 



1 Fossil Botany, p. 146. 



2 Potonie, Lehrbuch, p. 102. Mr. Kidston has shown me specimens of Oligocarpia 

 Gutbieri in which the line of dehiscence was clearly seen running radially down the 

 central face of the sporangium. The annulus could not be reduced to a single row of 

 cells. Probably the type had a pluriseriate annulus like other Palaeozoic Ferns (compare 

 Kidston, Phil. Trans., Ser. B, vol. 198, p. 188 ; also Scott, Progresses Rei Botanicae, 

 vol. i., p. 184). It may, however, be remarked that a division of the cells of the annulus 

 appears as an occasional irregularity in sporangia of living species of Gleichenia, a distant 

 suggestion of a pluriseriate annulus in the ancestry. 





