254 APPENDIX. 



Vacciniacece and Ericaceoe. 



There is no endemic genus of either of these orders, and the species number only 

 thirty ; but with one exception the species of the Vacciniacege are endemic, and forty- 

 nine out of fifty-eight Ericaceae are not known to occur outside of our boundaries. It 

 is noteworthy, too, that only four genera out of thirteen belonging to the two orders 

 are restricted to America. The special feature of these plants is that they form a very 

 prominent part of the shrubby element of the alpine flora. Associated with such 

 Andine genera as Macleania, Satyria, and Cavendishia are the wider spreading Vac- 

 cinium, Gaultheria, Arctostaphylos, and Arbutus. Pernettya and Bejaria have a wider 

 range in America, and the former reappears in New Zealand and Tasmania ; the latter 

 is the only one in our flora belonging to the tribe Rhododendreae. Of the herbaceous 

 Pyrolese, two out of three genera, Pyrola and Chimaphila, find their southern limit in 

 the mountains of South Mexico and Guatemala respectively. 



Lennoacece. 



A singular group of herbaceous root-parasites, of which three genera and four or 

 five species are known. Pholisma arenarium, the only species found outside of Mexico, 

 is a native of the country near San Diego and Monterey, California, and apparently 

 very local. Indeed all of them seem to be rare and local. In habit and aspect they 

 are not unlike the Monotropese and Orobanchacese, from which they differ in having 

 a multicellular ovary and other characters. There is no other order of parasitical 

 plants so restricted in area. 



Asclepiadece. 

 This chiefly tropical order is strongly developed in South Africa, and more so in 

 North America than in any other north temperate region, especially in the Texano- 

 Mexican region. North of Mexico there are nineteen genera represented by nearly 

 100 species; from North Mexico we have already fifty- two species belonging to ten 

 genera, and from South Mexico 100 species belonging to seventeen genera. The 

 tropical part of our area would seem to be singularly poor in this order, though no 

 doubt many more exist than have been collected. In the West Indies, too, there are 

 not many ; yet they abound in Brazil. Two of our genera, Vincetoocicum and Mars- 

 denia, have a wide range ; of Asclepias there are two African species ; the rest are 

 restricted to America and three of them to Mexico. Upwards of eighty of the Mexican 

 species belong to the genera Asclepias and Gonolobus in about equal numbers. Six 

 genera exhibit a north-western extension and the same number a north-eastern, while 

 the numbers of species are respectively twenty-three and four. Trichosacme, Lachno- 

 stoma, Polystemma, Fimbristemma, Nephradenia, JEnslenia, Blepharodon, Melinia, and 

 Oxypetalum are each represented by a single species, though only two of these genera 

 are monotypic. 



