LYGINODENDRON 373 



assumed a pseudo-polystelic structure. These anomalies, 

 though only found in some specimens of Lyginodendron 

 oldhamium, are interesting, not merely as an example 

 of the plasticity of structure which the formation of 

 cambium gives to a plant, but because they reappear, 

 apparently as constant features, in some allied fossil 

 stems. 



2. The Leaves. — We have now to consider the 

 evidence as to the nature of the leaves of Lyginodendron 

 oldhamium. Almost every specimen of the stem of 

 that plant is surrounded by a mass of finely divided 

 foliage, the stalks and leaflets of which are cut in every 

 direction by the plane of section. A good example is 

 shown in Fig. 130, from a photograph. The main 

 petioles of the leaves associated with the Lyginodendron 

 stems are of large size, reaching a centimetre in 

 diameter ; they are often found branching, and the 

 successive branches diminish in size, the ultimate 

 ramifications being quite slender. The smallest of 

 these are sometimes found irr connection with the 

 leaflets, which are deeply lobed, with veins diverging 

 from one another at an acute angle. The material 

 with structure preserved can only be studied in sections, 

 and is more or less fragmentary, so that it is impossible 

 to reconstruct, from it alone, a complete picture of the 

 form of the highly compound leaf. Enough, however, 

 is shown to enable us to identify these petrified 

 specimens with certain fronds preserved as impressions, 

 in which the whole configuration is manifest, and there 

 is now no doubt that the foliage in question is identical 

 with that of Sphenopteris Honinghausi, a form described 



