Flora of Southeastern Washington. 



PHYLUM I. PTERIDOPHYTA. Fern Plants. 



Plant containing woody tissue and vessels in the stem 

 and producing spores asexually which, on germination, 

 develop very small structures called prothallia, on which 

 are borne the sexual reproductive organs from which the 

 asexual plant is developed. The sexual plant is rarely 

 collected, and the classification is based mainly on the 

 characters of the asexual plant. 



Class I. FILICINEAE. 



Plant highly organized, vascular, with green usually 

 large leaves; spores borne within the tissue of, or in 

 modified hairs on, modified or unmodified foliage leaves; 

 stem solid, underground (in ours). 



Family 1. POLYPODIACEAE. 



Sporangia stalked, surrounded by a more or less complete 

 vertical annulus and bursting transversely; fruit dots on the 

 backs or the margins of the leaves, with or without indusia. 



Indusium none; fruit dots roundish. 1. Phegopteris, 2. 



Indusium present. 



Fruit dots with marginal false indusia formed of the 

 more or less altered edge of the leaf. 

 Sporangia on a marginal vein which connects 



the ends of the lateral veins. 2. Pteridium, 2. 



Sporangia at or near the ends of unconnected 

 veins. 

 False indusium continuous. 3. Pellaea, 2. 



False indusium not continuous. 4. Cheilanthes, 2. 



Fruit dots on the lower surface or margin of the 

 leaves, each with a special indusium. 

 Fruit dots linear or oblong; indusium more than 



twice as long as broad. 5. Athyrium, 3. 



Fruit dots roundish; indusium less than twice as 

 long as broad. 

 Indusium conspicuous, peltate. 6. Polystichum, 3. 



Indusium inconspicuous, not peltate. 



Veins of pinnules pinnately branched. 7. Woodsia, 3. 

 Veins of pinnules dichotomously branched. 8. Filix, 4. 



2 I 



