350 



23.— POLYPODIUM. 



Key to species. 



1. Fronds entire ... 



Fronds pinnatifid or once or more 

 pinnate 



2. Fronds dimorphic, fertile ones under 



6 inches long 

 Fronds not dimorphic ... 



3. Fronds very coriaceous 



Fronds papery 



4. Fronds under 4 inches long and under 



4 lines broad 

 Fronds more than 4 inches long and 

 4 lines broad 



5. Under side of fronds closely woolly ... 

 Under side of fronds covered with 



long soft hairs 



6. Fronds 2^ to 3 inches long, 2 to 3 lines 



broad 

 Fronds 2 inches long, 1^ to 2 lines 

 broad 



7. Fronds 3 to 4 inches long, 1 to H line 



broad, tomentum loose 

 Fronds 2 to 3 inches long, 2 to 2^ lines 

 broad, tomentum thick 



8. Under surface matted with cottony or 



woolly tomentum ... 

 Under surface not matted with woolly 

 hairs 



9. Stalks close together with a tuft of 



lanceolate brown scales at the base 

 Stalks distant without scales at the 

 base... 



10. Substance thin ; all or main veins 



distinct 

 Substance thick ; all veins obscure ... 



11. Sori large in single rows 

 Sori medium, scattered 



12. Fronds i to 1 foot long, |^ to 2 inches 



broad 

 Fronds 2 to 4 inches long, ^ to 1 inch 

 broad 



13. Sori small and copious, scattered 



irregularly ... 

 Sori large in irregular rows ... 



14. Main veins very distinct, veinlets 



reticulated ... 

 Main veins not distinct, veinlets not 

 reticulated ... 



15. Fronds pinnatifid 



Fronds once or more pinnate ... 



