270 STUDIES IN FOSSIL BOTANY 



It would be quite useless for us to go into the 

 distinctive characters of these provisional genera, which, 

 while they are of the greatest use to those working 

 practically at fossil floras, tell us nothing by themselves 

 as to affinities. It will be sufficient to explain two 

 or three of the principal generic names, which will 

 frequently recur in our subsequent descriptions. 



One of the largest of the artificial genera is that 

 named by Brongniart Pecopteris, which includes many 

 of the most striking Carboniferous " Fern-fronds," and is 

 of special interest, because a good deal is known as to 

 the fructification and anatomical structure of various 

 plants which possessed this type of leaf. It is certain 

 that some of its members were seed-bearing plants, but 

 there is still a strong probability that others were true 

 Ferns. The characters are thus given by M. Zeiller, 

 whose diagnosis I have somewhat abridged : — '' Fronds 

 generally tripinnate, often quadripinnatifid or quadri- 

 pinnate, more rarely bipinnate only. Rachis of diverse 

 orders naked between the pinnae, or bearing pinnules 

 between the latter. Pinnules attached to the rachis by 

 their whole breadth, usually very broad, contiguous, 

 sometimes more or less confluent, with parallel or 

 slightly convergent margins, usually entire, more rarely 

 lobed or dentate ; apex usually obtuse, sometimes 

 acute. Median nerve distinct, extending almost to 

 the apex of the pinnule ; secondary nerves pinnately 

 arranged, always springing from the median nerve, with 

 which they make a wide angle, and not directly from the 

 rachis ; sometimes simple, sometimes dichotomous." 1 



1 Bassin houiller et permien d'Auti/n ei (fEpinac, Flore fossile, Part i. 

 1890, p. 41. 



