MOUNTAIN ELOEA OE SOUTH MEXICO AND CENTEAL AMEEICA. 299 



Species. 



Endemic. 



504 



Extending to 



North 

 America. 



17 



South 

 America. 



19 



Andes 

 only. 



39 



N. and S. 

 America. 



Beyond 

 America. 



17 



America 83 = 13-8 per cent. 



Endemic 504 = 83*4 „ 



Of wider range . . 17= 2*8 „ 



Total 604 100-0 



The description at p. 145 conveys a very good idea of the vegetation of the peak of 

 Orizaba, and the preceding analysis gives a clue to the relationships of the mountain 

 flora of South Mexico and Central America generally. North Mexico is excluded 

 because it clearly belongs to a distinct subregion extending northward into the central 

 territories of the United States. For the purpose under consideration we have drawn up 

 the foregoing list of all the plants in our Enumeration, recorded as occurring at altitudes 

 of 8000 feet and upwards, from data on the labels of the various collectors. It will be 

 understood that this list is merely a sample of the flora, and it might easily be extended 

 by including the species which we know from other sources * grow above the limit 

 named, to say nothing of those which are evidently mountain plants, though we have 

 no actual authority for it ; but under any circumstances we could not make the list 

 approximately complete, therefore it seems better to restrict it in the manner stated. 

 On the other hand, it is probable that some of the plants included do not ascend quite 

 so high as 8000 feet, notwithstanding that the range given is up to that altitude. 



The figures in this analysis are perhaps the most interesting we have obtained, for they 

 show, more distinctly than those of the general table even, the strong southern affinity 

 of the flora of South Mexico. We also see what a large proportion of the generic types 

 of the highest zone of vegetation are of wide range. Very few indeed of the peculiarly 

 American or peculiarly Mexican forms reach the altitudinal limits of vegetation. Such 

 genera as Clusia, Amicia, Calliandra, Pleroma, Miconia, Begonia, Ravnia, Psychotria, 

 Myrsine, Ardisia, Achimenes, and many others occur only in the lower part of the range 

 indicated. 



* Thus, on referring to the Sketch of the Vegetation of the Peak of Orizaba (p. 145) we learn that the 

 additional genera Tilia, Cratcegus, Cotyledon, Chamcedorea, Agave, Smilax, Tillandsia, Tigridia, ArundinaHa 

 and others ascend to above 8000 feet ; and the number of orchids would have been vary much higher had we 

 included all those recorded above 8000 feet by Eichard and Galeotti (see p. 303). 



biol. cents. -ameb,, Bot. Vol. IV., December 1887. 2 r 



