280 APPENDIX. 



Among the remaining exclusively American genera within our limits we may mention 

 the broad-leaved Pharus (Panicese), Tripsacum, next Euchlcena in Maydese, Luziola in 

 Oryzeee, Hilaria in Zoysiea?, Bouteloua in Aveneae, Monanthochloe, Bissanthelium, 

 Orthoclada, Zeugites, and Uniola in Festucese, and Chusquea and Guadua in Bambusae ; 

 nearly all of them very distinct genera. 



With regard to the extra- American distribution, fifty-nine of the genera and thirty- 

 six of the species are widely spread. Four genera, namely, AnthepJiora, Olyra, Trachy- 

 pogon, and Ctenium, are only represented in Africa ; Olyra by one species, probably the 

 common American 0. latifolia. Distichlis thalassica is common on the coast of South- 

 eastern Australia, but not recorded from elsewhere in the Old World. In conclusion, 

 the interrupted distribution of Phleum alpinum merits notice. This grass inhabits the 

 Peak of Orizaba at 10,000 to 12,000 feet ; the Andes of Chili to Fuegia ; the alpine 

 and arctic regions of North America, Europe, and Asia. 



Filices and other Vascular Cryptogams. 



The distribution of the genera and species of sporiferous plants is generally much wider 

 than that of seminiferous plants, being limited apparently by climatal conditions only ; 

 and where the conditions are favourable, as in some regions of Mexico and Guatemala, 

 in New Zealand, and other parts of the world, large numbers are found in comparatively 

 small areas. A considerable degree of humidity is, of course, one of the indispensable 

 conditions for the majority of ferns, but, as will presently be shown, certain genera 

 affect dry regions. We allude now more particularly to the ferns. Taking the genera 

 as circumscribed in Hooker and Baker's ' Synopsis Filicum,' there are, including a few 

 recent new ones, about eighty, forty-eight of which are represented in Mexico and 

 Central America, and forty-one of them in South Mexico alone, where the number of 

 species known is 380. On the same basis, the total number of species of Ferns now 

 known is, as Mr. J. G. Baker informs us, approximately 3000 ; and our total is 545 ; 

 so that South Mexico and Guatemala together shelter one sixth of the species of the 

 whole world. 



As previously explained (vol. iii. p. 589), Fournier monographed the Mexican ferns. 

 Here, as in the grasses, he founded a large number of species which are not recognized 

 as such in this work. Thus, for Mexico alone he defined 605 species against our 545 

 for Mexico and Central America together. However, with the exception of species, we 

 obtain very similar results. Out of his 605, 178 were peculiar to Mexico ; and of the 

 427 common to Mexico and other regions, 230 were found in the Andes, 139 in the 

 West Indies, 59 in Venezuela and Guiana, and 117 in Brazil, most of them as far south 

 as Rio Janeiro. 



Of the forty-eight genera within our boundaries only one, the monotypic Llavea, is 

 endemic, and only three others, namely, Hypoderris, Dictyoxiphium, and Dancea, are 

 peculiar to America. Besides the Nicaraguan Hypoderris, there is one other species 



