OLD-FASPIIONED FERNS 257 



veins") present different patterns, sometimes being 

 parallel to one another or divergent (veins "free"), or 

 uniting here and there in a netted fashion (veins 

 "reticulated"). 



457. Since the sporophytes of ferns are long-lived 

 they delay the formation of their spores, this sometimes 

 not taking place for a few years (or many years in tree 

 ferns). In the more primitive ferns the spores develop 

 from internal cells (as in Anthoceros of the Bryophyta), 

 but in the higher forms they are produced in superficial 

 sporangia. 



458. On account of the dominance of the sporophyte 

 its structure has been emphasized in the systematic 

 classification of the ferns, although some consideration 

 has latterly been given to gametophyte characters. 

 About 3800 species of Ferns have been described, and 

 they are widely distributed throughout warm and tem- 

 perate regions. 



459. There are two classes of Ferns, as follows: 

 1. Old-fashioned Ferns (Class Eusporangiatae) in which 

 the spores develop from internal cells. 



Fig. 133. — Ophioglossum. Fig. 134. — Angiopteris 



(Marattiales) ; develop- 

 ment of sporangia. 



460. Here are the Adder-tongues (Order Ophio- 

 GLOSSALES) by many botanists regarded as the lowest of 

 the Ferns, and not very distantly related to Anthoceros 

 of the preceding phylum. Here too are placed the 



