104 NOTES OF A NATURALIST. 



probably attribute the chief characteristics of the flora. 

 With scarcely an exception, the species of this zone 

 are stunted in growth, rising but a few inches from 

 the surface, but have much developed prostrate or 

 creeping woody stems, or underground rhizomes. 

 Compared with the middle, or temperate, zone, the 

 species generally belong to the same natural groups. 

 Some of the families, however, which are characteristic 

 of the middle zone, such as Loasacecs, Verbenacece, and 

 SolanacecB, do not appear to reach the higher region. 



Of forms characteristic of the Alpine region of 

 mountains in the Old World I observed several ; e.g. 

 Geranium, Astragalus, Valeriana, Draba, a saxifrage, 

 and a very small gentian. 



To sum up my impressions as to the flora of the 

 western slopes of the Cordillera, I should say that it 

 appears to be naturally divided into three well-marked 

 zones. The lower, or subtropical, extending to about 

 eight thousand feet above the sea, characterized by 

 deficient rainfall, moderate heat continued throughout 

 the year, and a complete absence of cold, the ther- 

 mometer rarely falling below 50°. The species here 

 mainly belong to genera characteristic of the flora of 

 tropical America, but, owing to the climatal conditions, 

 are limited in number, and do not include groups 

 requiring much moisture. 



The middle, or temperate, zone, extending from 

 about eight thousand to about thirteen thousand feet 

 above the sea, possesses a very varied flora which 

 includes many groups characteristic of the Andes, and 

 entirely or mainly confined to that range, with repre- 

 sentatives of numerous genera that are widely diffused 



