CHAPTER XXI 



OSMUNDACEAE 



The family of the Osmundaceae comprises three genera and 17 species 

 of Hving Ferns, according to Christensen's Index: viz. Todea (i species), 

 Leptopteris (7 species), and Osniunda (9 species): but some writers have 

 regarded Leptopteris as a section of the genus Todea, thus recognising onh' 

 two genera. The Family is of wide geographical distribution, and it extends 

 to both hemispheres. Osnmnda is cosmopolitan, but Todea and Leptopteris 

 are native in South Africa and Australasia. In point of time the Family 

 extends back to the Palaeozoic Period. The evidence for this is derived from 

 beautifully preserved stems such as those oiZalesskya and Tlianinopteris from 

 the Upper Permian of Russia, first described by Eichwald {Lethaea Rossica, 

 i, Stuttgart i860), and thoroughly examined by Kidston and Gwynne- 

 Vaughan (Fossil Osmundaceae, Trans. R. S. Edin. 1907 to 19 14). These 

 show undoubted Osmundaceous characters, but their fructifications are 

 unknown. On the other hand many sporangia of structure resembling those 

 of living Osmundaceae have been described from the Upper Carboniferous 

 strata; but as Seward remarks {Fossil Plants, ii, p. 325) it is not safe to assume 

 that these were borne on plants possessing the anatomical characters of the 

 Osmundaceae rather than of the Botryopterideae. However, fructifications 

 of undoubted Osmundaceous character have been traced to the Jurassic 

 Period, and even referred by Raciborski to the genera Osnmnda and Todea 

 (Engler's JaJirb. xiii, p. 7). He adds that they are so highly differentiated 

 that their origin probably dates back still earlier. Such comparisons both of 

 anatomical structure and of the fructifications suggest an early origin of the 

 Osmundaceous stock. They stimulate comparison with the Botryopterideae, 

 and point to a probability that a family of such antiquity as the Osmundaceae 

 should prove a valuable basis for comparison also with more modern Ferns. 

 It will be found that it does so, and indeed the living Osmundaceae hav-e 

 long been recognised as holding a unique position intermediate between 

 Eusporangiate and Leptosporangiate Ferns. The description of them in 

 detail will fully justify this preliminary forecast. 



External Characters 

 The living Osmundaceae are all perennials, with an upright, usually short, 

 radially constructed stock, which bifurcates occasionally (Frontispiece). The 

 axis is covered by the persistent bases of leaves, which are disposed upon it 

 in a dense spiral. It is attached to the soil by numerous dark-coloured roots, 

 which originate in close relation to the bases of the crowded leaves, and form 

 with them a massive investment which hides the upright and branching 



