CHAPTER XII 

 THE EVOLUTION OF PLANTS (Concluded) 



138. Evidences from Fossil Plants. — The study of fossil 

 plant remains has greatly enlarged our knowledge of 

 the course of plant evolution, filling in gaps derived from 

 the study of living forms, and affording new facts, not 

 disclosed by the study of plants now living. Like the 

 study of comparative anatomy and life histories, paleo- 

 botany teaches us that there has been a gradual evolu- 

 tionary progress from the simple to the more complex, but 

 it has also disclosed the fact that some of the complex 

 forms are much more ancient than had been inferred from 

 the study of living plants only. 



139. Discovery of Seed-bearing Ferns.— For example, 

 remains of seed-bearing plants, quite as highly organized 

 as those of to-day, are found far back in the earliest fossil- 

 bearing strata of the Paleozoic. Great forest types ex- 

 isted as early as the Devonian. Later in the Carboniferous 

 occur many seed-bearing ferns. These have been called 

 Cycadofilicales (cycadaceous ferns), or, by some, Pterido- 

 sperms. Recent studies have disclosed the fact that 

 most of the fossil plants from the Carboniferous coal- 

 bearing strata, formerly thought to be ferns, are not even 

 cryptogams, but are these fern-Hke seed-bearing plants. 

 The best known pteridosperm is Lyginodendron oldhamium 

 (Fig. 86), first described from fossil leaves, in 1829, as , 

 a tree-fern, under the name Sphenopteris Hoeninghausi. 

 After investigations extending over nearly 90 years, "we are 



