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TEXTBOOK OF BOTANY 



Fig. 361. Two Devonian land plants (A-B) and a modern one (C) with some- 

 what similar characteristics. A, Rhijnia; B, Psilophijton; and C, Psilotum a fern- 

 like plant of tropics often cultivated in conservatories. Restorations by Kidson 

 and Lang (A), and by Dawson (B). 



Ancestral forms of the ferns appeared in the later Paleozoic. Not all 

 the representatives were large, but again the woody species seem to 

 have been most abundant. The leaves bear a close resemblance to those 

 of modern ferns, but several differences in stem structure and in repro- 

 ductive organs are evident. Some of these ferns were heterosporous, and 

 others were homosporous. 



For many years all the fossil leaf imprints and carbonized leaves that 

 resembled fern leaves were thought to be ferns; but evidence is con- 

 tinually appearing that a number, perhaps a majority, of the fern-like 

 leaves belonged to plants that bore true seeds: the Pteridosperms (Fig. 



