MAXON STUDIES OF TROPICAL AMERICAN FERNS. 27 



specimens, with the idea of fixing more exactly than is possible by 

 description alone the characteristic points of difference. 



In conclusion, notes upon the several West Indian species to be 

 excluded from this genus are presented. 



The species as here treated may be separated by the following 

 artificial key. The specimens listed are either in the V. S. National 

 Herbarium or the herbarium of the New York Botanical Garden, 

 unless otherwise stated. 



KEY TO THE SPECIES. 



Rhizome sarmentose; fronds uniserial (,§ Rumohra) 2. P. adiantiformc. 



Rhizome erect or ascending; fronds cespitose (§ Eupolystichum), 

 Lamina subentire to deeply pinnatifid. 



Lamina snbentire, somewhat lobed at the base, the 



apex retuse 12. P . plaschnickianum. 



Lamina deeply pinnatifid below, the apex long- 

 attenuate 16. P. rkixophyllwn . 



Lamina once to thrice pinnate. 

 Normally once pinnate only. 

 Proliferous. 



A pex foliose, retuse 19. P. under wood H. 



Apex naked, flagelliform. 



Lamina linear, elongate 9. P. ilicifolium. 



Lamina broader and shorter, lanceo- 

 late to linear-lanceolate. 



Fronds difform, the fertile con- 

 spicuously shorter and long- 



stipitate 15. P . rhizophorum. 



Fronds conform, of equal size. 



Pinnas straight or nearly so, 

 deeply erenate-lobulate, 



nonspinulose 7 . P. harrisii. 



Pinnae falcate, lightly crenate- 



serrate, spinulose 4. P. decoratum. 



N on proliferous. 



Stipe and rachis rather dark, closely covered 



with persistent chaff 17. P. ttruthionis. 



Stipe and rachis light-colored; chaff scant, 

 mostly deciduous. 



Lamina short, ovate to broadly ovate, 



long-stipitate 10. P. longipes. 



Lamina elongate, lanceolate to linear. 

 Plants delicate; margins of pinna 1 



erose-dentate 6. P. guadelou pen.se. 



Plants rigidly coriaceous; pinnae 



variously spinescent-serrate 1. P. triangulum. 



More than simply pinnate. 

 Xon proliferous. 



Pinnae unequally trifoliolate, the terminal 



division narrow IS. P. tridens. 



Lamina tripinnate or quadripinnatifid 11. P. muricutui* 



82464—09 3 





