22 BRITISH EOCENE FLORA. 



ScMzaaceee are represented hy a Lyrjodium allied to the recent L. paJmatum^ and identical 

 with a species from the Eocene Lignitic Series of America. In tiiis Fern the fertile 

 fronds have also been met with. A species of Aneimia is very abundant and beautifully 

 preserved at Bournemouth, and is also common to the Eocenes of America and Sezanne, 

 and possibly Aix-la-Chapelle. The most prevalent form, however, is Osmunda lignitum, 

 which is equally abundant at Bovey-Tracey, and of which 0. DoiuJcerly Carr., may 

 possibly be the stem. Of the other Ferns figured, one, if not two, certainly belongs to 

 Adiantum, ; and there are others upon which no determination can be hazarded. 



The Ferns seem to throw some light upon the physical condition and gi-adual 

 depression of the land in the Eocene period. At Bournemouth the lower beds, met with 

 towards Poole, are supposed to contain a wooded and more or less hillside flora, and 

 Ferns are there represented only by a climbing Lygodium. In the beds further east, 

 near the Pier, which contain a more luxuriant vegetation, we find the delicate Gleichenia, 

 both species of Phef/ojjteris, and Osmunda. These, I believe, required a warm, moist, 

 shady situation. We next find the large Chrijsodiim, Osmunda, ]\feniphyUum, and 

 Pteris, mingled with masses of Aroids, &c., which would require a still more moist 

 habitat. Finally, in the most eastern and newest beds of the freshwater series, we meet 

 with masses of PoJypodiea, which probably grew at the sea-level in company with a 

 decidedly swamp vegetation. 



Of all the Ferns described, only four were previously known as British, and two of 

 these were supposed to be from the Miocene. Three were known from the American 

 Eocene, four from the Aquitanian and Tongrian stages of Western Europe, and one from 

 Sezanne ; the rest are new. In addition to these, there are several other Ferns, which are 

 too indistinct to be figured. 



Von Ettingshausen, in his work on Tertiary plants, has found it necessary to invent a 

 distinct terminology for Ferns. ^ His explanation of the types of venation, and the terms 

 he distinguishes them by, so far as he employs them in the present work, will be useful 

 here. 



" The simplest venation in Ferns is the Hyphopteris (fig. 1), in which each division 

 of the frond is traversed by only one vein. 



" When the veins, and consequently also the divisions of the frond, are arranged in a 

 compact pinnate or pectinate order, then the HypJwpteris type becomes the Craspedopteris 

 (fig. 2). In this case the rachis maybe regarded as the midrib or primary vein, and the 

 midribs as secondary veins. This applies more particularly to the Craspedopteris vera, 

 where the secondary veins are mostly connected by parenchyma. When the veins are 

 disconnected, except at their base, it becomes Craspedopteris Ctenodes, e.g. Polybotrya 

 LecJderiana^ Mett. ; Ett., 'Farnkr.,' PI. xiii, figs. 5, C, &c. 



^ 'Die Farnkrauten der Jeztwelt,' Vienna, 1865. 



