THE FLORA OF NORTH MEXICO. 141 



Pinus edulis, with an undergrowth of Vitis incisa, Clematis pitcheri, TIngnadia speciosa, 

 &c. The constant presence of water in the larger valleys is indicated by the growth of 

 poplars and willows. 



^ The vegetation of the valley of the Upper Eio Grande and that of the country imme- 

 diately adjoining it on either side are strikingly different. Upon the tablelands which 

 spread out beyond the mountain-barrier is a great variety of plants not met with in 

 the more fertile valley, including Fouquieria splendens, Larrea mexicana, Flourensia 

 cernua, Bhus microphylla, Condalia obovata, Koeberlinia spinosa, and various species 

 of Krameria, Ephedra, Yucca, Opuntia, Echinocactus, Mamillaria, and Cereus. Of 

 the numerous herbaceous and half-shrubby plants of this region Cevallia sinuata, 

 Greggia camporum, Eriogonum abertii, and several species of Balea may be mentioned. 

 Composite are especially abundant, prominent among them Baileya multiradiata, 

 Bahia absinthifolia, Porophyllum scoparium, Psathyrotes scaposa, Hymenatherum 

 acerosum, Townsendia strigosa, Calycoseris wrightii, Stephanomeria minor, and Bafi- 

 nesquia neo-mexicana. The Nyctaginese are represented by Selinocarpus, Boerhaavia, 

 and others; and the principal grasses of the region are of the kinds known as 

 " bunch-grass," and belong to the genus Bouteloua. On the margin of the tableland, 

 bordering the valley where it is broken by deep ravines, the sandy bluffs are clothed 

 with chaparral made up chiefly of mesquit (Prosopis juliflora) and thorny acacias. 

 Chilopsis linearis is frequent in the dry pebbly watercourses ; and besides many of the 

 tableland plants already mentioned, there are others which are peculiar to these locali- 

 ties, such as Bithyrea wislizenii, Abronia mellifera, Gilia longiflora, Lepidium alys- 

 soides, Gaillardia pinnatijida, Palafoxia hooJceriana, and Tetraclea coulteri. In the 

 valley of the Rio Grande dense growths of willows and poplars are frequent. Pro- 

 sopis pubescens often occupies large tracts, with a thick undergrowth of Baccharis 

 mlicina. In low saline places Obione canescens abounds, and Pluchea borealis on the 

 higher ground. A number of coarse Composite inhabit the valley, such as Zexmenia 

 encelioides, Coreopsis car daminm folia, and Aster spinosus, often forming dense matted 

 masses. Fendleria rupicola, Mortonia crassifolia, Glossopetalum spinescens } Ayenia 

 parvifolia, Bouvardia hirtella, Tecoma stans, and Zexmenia brevifolia are interesting 

 plants of this region. The higher mountains of the Organ range have a subalpine 

 vegetation and bear a scattered growth of oaks and pines, beneath which flourish a 

 number of herbaceous and shrubby plants similar to those on the loftier ranges 

 westward. 



Passing to the Sierra Madre range, Carpochaetes bigelovii, Anemone caroliniana, 

 Streptanthus linearifolius, Pentstemon torreyi, and P. fendleri are characteristic plants 

 of the lower rocky swells. Of shrubby plants various species of Ephedra are the most 

 conspicuous. Fraxinus velutinus and Juglans rupestris border the streams, and 

 Anemiopsis calif ornica appears in humid situations. The mountain oaks and pines are 

 chiefly Quercus emoryi and Pinus edulis, though in certain localities there is larger 





