DISTEIBUTION OE THE MOEE PEOMINENT NATTJEAL OEDEES. 255 



Gentianece. 

 In this order, as in many others, temperate wide-ranging genera overlap and inter- 

 mingle with American ; thus Leianthus and Lisianthus with Gentiana and Erythrcea ; 

 and the widely-spread Gentiana amarella reaches North Mexico. Geniostemon is 

 the only endemic genus. Voyria is a genus of small leafless herbs widely spread in 

 tropical America, and represented by one endemic species in west tropical Africa. 



Polemoniacece. 



Polemonium is represented by a few species in temperate Europe and Asia and Phlox 

 in North-eastern Asia, otherwise the order is wholly American and chiefly western, 

 extending southward to Chili. North of Mexico there are four (or five, if Collomia be 

 retained) genera and 133 species, whereof sixty-three are Californian. The genus 

 Phlox is the only one common in the Atlantic States, where there are ten or twelve 

 species. In Mexico and Central America there are seven genera, including the two 

 which extend to the Old World, and the endemic monotypic Ponplandia. Cobcea 

 reappears in the Andes, and the remainder are both North American and Chilian. 

 With few shrubby exceptions, this order is herbaceous. 



Hydrophyllacece. 



This wholly herbaceous order is essentially American, and especially numerous in 

 California, where there are twelve genera and sixty-one species out of totals of seven- 

 teen and 150. Excepting the singular South-African monotypic Codon, and the rare 

 Japanese monotypic Ellisiophyllum, all the genera are American, and fourteen out of 

 fifteen are restricted to America. Five genera and fifteen species occur in the Atlantic 

 States; but of these Nama is only represented in South Forida by the widely-spread 

 N. jamaicense ; and all the genera except Hydrolea, the one widely spread in the 

 tropics of the Old World, are also western. Three of the northern genera extend to 

 Chili, where there are about eight species, including Phacelia circinnata, which ranges 

 from British Colombia to the Straits of Magellan. Within our limits there are five 

 genera, including Hydrolea, not one of which is endemic ; and thirty-two species, of which 

 sixteen are endemic in the northern division, and eleven extend into North-western 

 America, against one into eastern. Three of the commoner species extend to the West 

 Indies, where only one endemic species of the order, Hydrolea nigricaulis, a Cuban 

 plant, is known to exist; and one of the same species reaches Brazil, where only 

 Hydrolea and Wigandia are represented. Seventeen of the Mexican species belong to 

 Nama ; and only Hydrolea and Wigandia have been found south of Honduras. The 

 latter genus is restricted to the mountains of the tropical parts of America, where, 

 however, it has a wide range. 



