IQI2] 



WATSON— PLANT GEOGRAPHY OF NEW MEXICO 



205 



Sonoran to Lower at once. On the other hand, there appears on 

 the rock cedars and other plants characteristic of the next forma- 

 tion. This association is also sDread over the 



mesa 



river and over the lava field where the species are identical with 

 those of the sandy clay of the mesa, but some, especially Gutierrezia, 

 are stunted. Here also are a few cedars, Rhus, and other mountain 



plants. 



Id seems to receive slightly more 

 \ the mountains and ascends one 

 mouths of the canons, a new ph 



Fig. 2. — At the base of the Sandia Mountains: Opuntia arborescens society; 

 Rhus trifoliata appears in the center, and in the background on the rocky slope are 

 black looking clumps of Nolina. 



Opuntia arborescens ', whose cylindrical stems, 6-8 ft. tall, bear 

 beautiful deep rose blossoms in June, and yellow fruit the remainder 

 of the year (figs. 2 and 3). These cacti form dense thickets, which 

 with Yucca glauca, Croton texensis, and Fallugia, which again 

 become abundant here, are quite as characteristic features of these 

 fans as the more abundant Gutierrezia and grasses. 



CEDAR FORMATION 



Next 



the dominant plant. 



formation of which Juniper us monosp 

 East of Albunueraue it is confined 



