xx] 



PAEKERIACEAE 



297 



Parkeriaceae. (Oeratopteris.) 

 The almost spherical and scattered sporangia are character- 

 ised by the peculiar form of the vertical annulus, which is 

 composed of numerous cells differing in their greater breadth 



A 



Fig. 231. A, A'. Dipteris quinquefurcata (type-specimen in the Kew 

 Herbarium). 

 B, C, E, G. D. conjugata. (C, \ uat. size.) 

 D. Pohjpodinm quercifolium. 

 F. Dipteris WalUcMi. 

 (D, after Luerssen.) 



and smaller depth from those of a typical annulus. Exannulate 

 sporangia have been described, while others occur showing 

 different stages between a rudimentary and a complete ring. 

 The single species of Oeratopteris, C. thalictroides, is an annual 

 aquatic fern widely spread in tropical countries ^ 

 ' Kny (75) ; Ford (02) ; Goebel (91). 



