SECT. vin. OSMUNDINE^E. 363 



ovate, instead of being cup-shaped, with much swollen 

 convex valves, meeting by their edges but not com- 

 pressed towards the apex. 



The Schizseinese are many of them climbing ferns, 

 and for the most part tropical. Lygodium articulatum 

 climbs trees in New Zealand to the height of fifty or 

 one hundred feet, and its tough wiry stems are used for 

 cordage. In one group of this order, represented by 

 Lygodium, the sporangia are disposed at the back of 

 the frond in imbricated marginal spikes, formed by a 

 transformation of the ultimate pinnae. In the other 

 division, represented by Schizsea, the fruitful spikes are 

 really on the under-side of the frond, but the frond 

 being reversed they seem to be on the upper. 



The Ceratopteridinese, sometimes called Parkeriacese, 

 are tropical aquatic ferns, whose sterile fronds, which 

 are membranaceous, with a thick vascular footstalk, 

 float on the surface of the water, and by the time these 

 are nearly decayed the fertile fronds are perfected. 

 The latter are more erect, repeatedly divided and forked, 

 the divisions being linear. There is only a single genus, 

 Ceratopteris, which has continuous sori occupying the 

 longitudinal veins at the edge of the frond, and covered 

 by the indusioid margin. The sporangia have a very 

 broad incomplete ring, and connect the ringless ferns 

 with the group which possess them. The spores are 

 triangular, and marked with three sets of concentric 

 ridges. 



The order Osmundinese contains the Osmunda regalis, 

 considered to be the finest of all European ferns, which 

 is common throughout Great Britain in wet spongy 

 soils, and appears to be the only species of the group that 

 is European. The fronds grow in tufts from a thick 

 woody caudex, which branches and extends widely by 

 the formation of lateral crowns, but, if impeded, it elon- 

 gates and rises in an erect position to the height of two 



