20 VEGETATION OF A DESERT MOUNTAIN RANGE. 



reticulata, Baccharis sarothroides (batamote), Franseria ambrosioides, 

 Lycium fremontii, Verbesina encelioides, and Bebbia juncea. 



In the canons and arroyos large enough to have a heavy flow of 

 storm water but not large enough to have even pools of water which 

 are constant throughout the year, there may be found several additional 

 species of plants which also occur on the sandy flood-plains of the 

 largest canons. Prominent among these are Chilopsis linearis, Hymeno- 

 clea monogyra, and Baccharis glutinosa, all of which are large shrubs 

 or in the case of Chilopsis may attain the size of small trees. Also 

 characteristic of these sands are Franseria ambrosioides, Rumex hymeno- 

 sepalus, Euphorbia pediculifera, Clematis ligusticifolia, and Calyptridium 

 monandrum. 



In the largest canons of the south side of the Santa Catalinas it is 

 possible to witness the occurrence of communities of mesophilous, 

 palustrine, and aquatic plants which are limited in area but are made 

 up of species which stand strongly in contrast with the predominant 

 forms of the bajadas. The existence of streams and pools adjacent to 

 rocky slopes makes it possible in several places for Callitriche and 

 Isnardia to grow within 20 feet of Carnegiea and Fouquieria. 



At the mouth of Soldier Canon the rocky slopes of the streamway 

 are clothed with typical bajada plants together with a few forms which 

 are particularly abundant on cliffs and in rocky situations, both in the 

 larger mountains of the region and in the volcanic hills. Among the 

 latter are Opuntia bigelovii, Hyptis emoryi, Lippia wrightii, Anisacan- 

 thus thurberi, Encelia farinosa, Eriogonum wrightii, Chrysoma laricifolia, 

 and Crossosoma bigelovii. Among the boulders bordering the stream- 

 way are Janusia gracilis, Plumbago scandens, Maurandia antirrhini- 

 flora, Mimitanthe pilosa, and Stemodia plumieri, as well as occasional 

 individuals of several species which are common away from streams 

 at elevations of 4,000 to 5,000 feet, as, for example, Dasylirion wheeleri, 

 Nolina microcarpa, Erythrina flabelliformis, Ingenhousia triloba, and 

 Mimosa biuncifera. When the sands of the arroyo have not been 

 recently scoured by floods they support scattered individuals of Ama- 

 ranthus palmeri (celite), Cassia leptocarpa, Nicotiana trigonophylla, 

 Bebbia juncea, Hymenoclea monogyra, Franseria xanthocarpa, Asclepias 

 linifolia, Baccharis sarothroides, Mentzelia gracilenta, and Carduus sp. 



In Ventana, Bear, and Sabino Canons it is possible at all times of 

 the year to find small colonies of palustrine and aquatic plants, and 

 the vicinity of such localities is the optimum habitat for Prosopis and 

 Populus. An underflow passes out at the mouth of Sabino Canon which 

 is heavier and more constant than that of any other canon in the range; 

 this gives Sabino Canon its abundant mesophilous vegetation and also 

 causes the arroyo through which its flood waters reach the Rillito to 

 be occupied by a much richer stand of vegetation than is to be found 

 along any of the arroyos of the adjacent region. The sandy and 



