MEDULLOSEAE 



427 



In some cases, pinnae of a different form, without 

 a median nerve, and described under the name of 

 Cyclopteris, were attached directly to the rachis, and 

 may have been of a stipellar nature. These organs 

 are of the same kind as the " Aphlebiae," mentioned in 

 Chapter VIII. as occurring on the fronds of Ferns. 



In the genus Aletlw- 

 pteris the leaves are 

 likewise large, and bi- 

 to tripinnate, but here 

 the thick, usually oblong 

 pinnules are inserted on 

 the rachis by a broad, 

 decurrent base, and are 

 in some cases confluent 

 with one another. The 

 edges of each leaflet are 

 incurved on the lower 

 side. The median nerve 

 extends the whole length 

 of the pinnule, and is 

 prominent on its under 

 surface ; the secondary 

 nerves leave the median 

 one at a wide angle, and pass directly, with or without 

 dichotomy, to the margin (see Fig. 162). The habit 

 resembles that of the recent Marattiaceous Fern 

 A ngiopteris. 



In the case of both these so-called genera, founded 

 on the external characters of the leaf, there is now 

 good evidence that they belonged to stems of the 

 family Medulloseae, of which the structural characters 



Fig. 162. — Alcthopteris lonchitica (foliage of a 

 Mcdullosa). Part of frond. Reduced. From 

 a photograph by Mr. W. Hemingway. 



