262 



PLANT MORPHOLOGY 



widely distrilnited, while Helminthostachys, with a single species, is con- 

 fined to Polynesia and tropical Asia. The Ophioglossales are unknown as 

 fossils but constitute the most primitive order of Uving ferns. 



Sporophyte. Most of the Ophioglossales are erect terrestrial plants. 

 The stem is a short, upright, unbranched rhizome producing a few large 



Fig. 217. Ophioglossum calif ornicum, about one and one-half times natural size. 



leaves and numerous rather fleshy roots. Usually only one leaf is formed 

 each year. The smallest species of Ophioglossum and Botrychium are less 

 than 8 cm. tall, but several species of Botrychium may reach a height of 

 60 cm. Ophioglossum pendulum, an epiphyte of the Oriental tropics, has 

 a creeping stem and pendent leaves that are frequently 1.5 m. long. The 

 leaf of Helminthostachys is about 30 cm. in length. 



As a rule, the leaf blade of Ophioglossum is simple, while that of Botrych- 

 ium is pinnately divided (Figs. 217 and 218). The leaf blade of Helmin- 



