230 



Symmetrical clamps of Calamagrostis longifolia 6 feet high, their large 

 panicles bending gracefully outward, send their roots deep down into 

 the dry sand. 



Rings of Mulileribergia pungens are scattered over the flats here and 

 there. This grass spreads by underground stems, which grow continu- 

 ally outward, the older inner part dying, and disappearing, leaving the 

 bare sand surrounded by a circumference of living green. These cen- 

 trifugal circles are sometimes 10 feet in diameter, with the interlaced 

 purple panicles of the ring afoot wide. The rare Oxytenia acerosa, with 

 Blgelovia Wrightii, Heliotropium convolvulaceum, Dicoria Brandegei, An- 

 dropogon Torreyana, are some of the plants common in these dry rivers. 

 When we ride up these rivers of sand, sometimes a bright, green cotton- 

 wood, or Negundo, is met with, showing that water must be down deep 

 somewhere. How they managed to exist before their roots reached 

 moisture is an interesting question. El Late and Cariso, groups of low 

 mountains about 9,000 feet in altitude, produce a flora similar to one 

 another and very different from that of the plains from which they rise. 

 Pinus edulis and Juniperus occidentalis cover Cariso, and grow nearly 

 upon the summit of El Late. The characteristic vegetation is the same 

 as that of the La Plata and Animas of the same altitude. 



Upon the eastern slope of the Kocky Mountains, in the valley of the 

 Arkansas, the Cactacece, on account of their abundance and size, are a 

 prominent part of the vegetation. It was expected^ that the southern 

 latitude, low altitude, and dryness of Southwestern Colorado, with its 

 proximity to the cactus region of Arizona, would be favorable to the 

 growth of Cactacece, but the number of species is less than in the Ar- 

 kansas Valley, and the number of plants is very small. Only two spe- 

 cies to be added to the flora of Colorado make their appearance : an 

 JEchinocactus and a Cylindropuntia. The Cylindropuntm is found at alti- 

 tudes between 7,000 and 8,000 feet, and Echmocactm Wkipplei generally 

 does not grow in the lowest altitudes, so that the country along the San 

 Juan River has not a single additional species of cactus, and lacks very 

 nearly all the species of the eastern slope. The great beds of Opuntia 

 Missouriensis which cover the plains and parks of the eastern slope are 

 not found in Southwestern Colorado ; neither Opuntia arborescens nor 

 Cereus viridiflorns was seen, and no species is common. 



The genus Astragalus is represented by few species, and these are 

 not very abundant. They grow almost wholly above 6,000 feet altitude. 

 None of the species of Astragalus of Southwestern Colorado, with the 

 exception of A. loncliocarpus, appear upon the eastern slope. Twelve 

 leguminous plants were found which grow in Eastern Colorado, while 

 not more than eight species common to the plains of both eastern and 

 western slopes were seen. Few of the Leguminosce are very abundant. 



The shrubby Rosacece are in strong force and characteristic of the 

 flora of Southwestern Colorado from high to low altitudes. The spe- 

 cies common to both eastern and western slopes, the abundance of some 

 which rarely grow upon the eastern slope, together with those species 

 which here enter the limits of Colorado, give great prominence to the 

 rosaceous shrubs. 



The genus Eriogonum is well represented in species, and the plants 

 are very abundant, especially those of the annuals. Nine annual species 

 grow in the San Juan Valley ; in the Arkansas Valley but three are 

 found, and in Northern Colorado but one. 



At about 8,000 feet altitude, the common oak of Colorado is very 

 abundant, growing upon the bluff-sides and becoming a small tree in 

 moist locations. At lower altitudes, it is rarely seen, and is a small bush. 



