4 THE FERN ALLIES. 



were placed such diverse plants as the algje, fungi, liver- 

 worts, mosses, and ferns. None of these ever bear 

 flowers or produce seeds, but, aside from this, the 

 various groups differ as much among themselves as the 

 division as a whole differs from the flowering plants. 

 The ferns and fern allies are the most highly developed 

 of these plant families, and in structure are closely re- 

 lated to the simplest flowering plants. They, alone, have 

 true roots and stems with tissues specialized for different 

 functions. The presence of these specialized tissues — 

 the so-called fibro-vascular system — has caused these 

 plants to be called Vascular Cryptogams or Vascu- 

 lar Acrogens to distinguish them from the less-spe- 

 cialized mosses, algae, etc., composing the Cellular 

 Acrogens. 



Modern botany still accepts these divisions, though 

 the terms used to designate them have changed some- 

 what as they have become adjusted to our present 

 ideas of nomenclature. We now usually speak of flower- 

 ing plants as the Spermatopliyta, and of the ferns and 

 fern-like plants (the vascular acrogens) as the Pterido- 

 pJiyta. The mosses and liverworts are now the BryopJiyta, 

 and the rest of the cellular acrogens are spoken of as the 

 TJiallopJiyta. The fern allies, then, belong to the high- 

 est division of the flowerless plants, have stems in 

 which there are woody tissues and ducts, and, in 

 short, comprise all the Ptcridopliyta except the 

 ferns themselves, as shown by the accompanying 

 table of the orders represented in the North Ameri- 

 can Flora. 



