546 



FILICALES 



The sporangia of Mohria are radially constructed, the apex and base 

 being opposite (Fig. 302 D, E). In the other genera the sporangia are more 



or less curved, so as to be dorsiventral 

 this curvature is slight in Aneimia an< 

 Schizaea (Fig. 302 A, B, F, o), but ven 

 marked in Lygodium (Fig. 302 c). 



Here it will be well to introduce 

 a brief notice of certain fossil sporangia 

 which have been referred to this affinity, 



Senftenbergia (Pecopteris) elegans, Corcla. 

 A a small piece of sporophyll (|). = a spor- 

 angium (- 3 r 5 -). (After Zeiller, from Engler and 

 Prantl, Nat. Pflanzenfam.') 



the structure of those of living forms. 

 The best known of these is Sen/ten 

 bergia (Pecopteris) elegans, Corda, fro 

 the upper Carboniferous (Fig. 303) : i 

 corresponds to Schizaea both in th 

 disposition of the solitary sporangia 

 and in their form and mode of dehi- 



scence; but the annulus is composed of several cell-rows, and the terminal 



"plate" has not been observed. Zeiller points out, however, that this is not 



an absolute difference from living forms, for various species of Lygodium 



(a genus which has itself been traced back 



to the Cretaceous Period), have a partially 



double series of cells of the annulus, while 



the " plate " in living forms is often so 



small that a similar one in a fossil- 



impression might well escape detection. 1 



A second example is the genus Klukia, 



the fructification of a Pecopterid from the 



Jurassic, of which several species have 



been described by RaciborskL 2 Here the 



arrangement of the sporangia, their struc- 



ture, and line of dehiscence are as in 



Schizaea, there being only a single series 



of cells of the annulus (Fig. 304). In 



both of these genera of fossils it is to be 



noted that the sporangia are intra-marginal, 



11 r r i i i 



On the lower Surface Of the pinnule, but 



without any indusial protection, while there 



is no specialisation of the fertile pinnules. 



From such comparisons it would appear probable not only that the 



Schizaeaceous type is an ancient one, but that it sprang from plants with 



a Pecopterid type of frond, without differentiation of specialised fertile 



pinnules, and that the sporangia were intra-marginal, on the lower surface. 



^ Bull. Soc. Bot. de France, T. xxiv., p. 217. 

 2 Engler'' s Jahrb, , xiii., p. I, Taf. I. 



FIG. 304. 



Kiki\ exiiis (Phiii PP s). 



Fertile pinnule of last order, seen from 

 below (^). From the Jurassic of Krakau. 



