XVIII] CORYNEPTERIS 33 



formed a mechanical loop not unlike that oi Angiopteris (compare Fig. 404, 

 Chapter XX). Cut transversely the loop appears as a widening of the cells on 

 either side, with thinner regions between them. The orientation of the 

 sporangia thus constructed is evidently round a central point, with one 

 thinner region turned centrally the other peripherally. In fact they constitute 

 a simple uniseriate sorus, notwithstanding that each sporangium is pedicel- 

 late. The spores are again numerous : in the larger of the variable sporangia 

 they must have numbered about 1000. 



If the sporangial stalks were shortened and the sporangia thus grouped 

 were associated more closely together, the condition characteristic of Cory- 

 tiepteris would result (Fig. 334). This genus is believed to be closely allied to 

 Etapteris. Hitherto it is known only in the form of impressions. The leaves 

 were of Sphenopterid or Pecopterid type, and the narrow pinnules bore 

 each a single sorus of five or ten sporangia grouped round a common centre. 



B 



Fig- 334- A = Corynepteris Essenghi Andrae, from the Carboniferous 

 (Westphalian). Fragment of a fertile pinna. (x6.) B=C. coral/oides 

 Gutbier, from the Westphalian. Fragment of a fertile pinna. ( x 4.) 

 5' = sorus of the same species seen laterally. ( x 28.) (After Zeiller.) 



The annulus is here again a broad peripheral band, consisting of several 

 rows of cells. The annulus of each sporangium is in juxtaposition with that 

 of its next neighbour. It is as though a group like that of Etapteris were 

 condensed upon a common receptacle (compare Fig. 333, 3). It is in fact 

 a radial sorus, essentially of the Marattiaceous type. The existence of a 

 definite annulus to each sporangium makes it probable that the sporangia 

 were not actually coalescent, though closely grouped, otherwise the annulus 

 would be mechanically useless. These three examples suggest a possible 

 origin of the uniseriate sorus, from isolated distal sporangia. If the pedicels 

 bearing these were short and numerous, the sporangia would be disposed as 

 in Etapteris. If so much abbreviated as to bring the sporangia compactly 

 together, the receptacle would become a common one with the result as in 

 Corynepteris. Thus it would be possible to regard the uniseriate sorus as a 

 condensed and compacted tassel of branchlets each bearing a distal 

 sporangium. 



B. II 3 



