Marsiliaceae, Salviniaceae y 



Subtribe 4. Pteridinae. Sori on intramarginal vein- 

 anastomoses, covered by the indusial leaf margin. 



Only British genus (sorus with an additional inner 

 indusial ciliate flap) : Pteridium (= Pteris auct.). 



Tribe 5. Polypodieae. Leaves separating from 

 rhizome by definite absciss-layers. Indtisium absent. 

 Only British genus (sori circular) : Polypodium. 



Suborder 2. Hydropteridineae. Wall of sporan- 

 gium without ammlits. Spores of two kinds (hetero- 

 sporous). Macrospores borne singly in macrosporangia, 

 and each developing a female prothallus. Microspores 

 numerous in each microsporangium, and developing 

 minute few-celled male prothalli. 



Family i. Marsiliaceae. Rhizome of sporophyte 

 solenostelic with two rows of leaves. Sori enclosed in 

 special organs {sporocarps) which arise as branches of 

 the leaves. Female prothallus producing a single arche- 

 goniiim. 



Only British genus (leaves filiform) : Pilularia. 



Family 2. SALVINIACEAE. Rhizome of sporophyte 

 floating, haplostelic, with two or three rows of partly 

 submerged leaves, on which the sori, enclosed in ifidtisia, 

 are borne. Female prothallus producing several arche- 

 gonia. 



Leaves in two rows, deeply bilobed. True roots 

 presentf. *Azolla. 



Order 2. Ophioglossales. Fertile leaves with one 

 or more simple or pinnate branches bearing the bulky, 



t Cf the exotic genus Salvifiia which is rootless. 



