

FLOWERING PLANTS AND FERNS OF ARIZONA 21 



forests of the southern counties are rarely seen north of Salt River. 



The trees most commonly associated with the pines in southern 

 Arizona are Juniperus pachyphloea, Qaercus hypoleucoides, Arbutus 

 arizonica (madrono), and Qaercus gambelii. The large shrub Q. 

 dwersicolor is frequent in the forest and often forms extensive thickets 

 where trees are absent. Along the streams are found ALnus oblongi- 

 folia (alder), Acer negundo var. interius, Acer grandidentatum var. 

 brachypterum, and shrubby willows. 



In late summer the floor of the pine forests is richly covered with a 

 large ntmiber of species of root perennials, in which grasses, legumes, 

 and composites predominate. There are very few species of annuals. 

 and likewise none of the herbaceous perennials are active in the late 

 winter, at a time when the desert is often covered with flowering an- 

 nuals. Some of the commonest root perennials in the pine forests of 

 southern Arizona are: Pteridium aquilinum, Poa fendhriana, MvMen- 

 bergia virescens, Panicum bvlbosum, Potentilla svbviscosa, Lupinus 

 palmeri, Lathy/us graminifolius, Cologania longifolia, Apocynum andro- 

 saemifolium, Liihospermum mvtiiflorum, Monarda austromontana, 

 Hedeoma hyssopifolium, Houstonia urightii. S<>Ii/:lago sparsiflora, 

 Erigeron spp., Hymenopappus mexicanus } Helenium hoopesiij Tagetes 

 le m m o n i , and Ach illea la n idosa . 



In northern Arizona the pine forests are somewhat poorer in the 

 number of associated trees and in the variety of root perennials but 

 have a greater abundance of shrubs. The floor of the forest is much 

 more heavily carpeted with grasses in the northern counties, and young 

 pines are themselves more abundant. Large openings or parks, dom- 

 inated by grasses and sedges, are a characteristic feature of the forests 

 throughout the most heavily wooded part of the State. 



The commonest tree associated with the pines is the deciduous oak 

 Que reus gambdii, which seldom reaches more than half the height of 

 the taUest pines and is found singly or more often in close groups of 10 

 to 50 small trees. Another locally very abundant deciduous tree is 

 Populus tremuhndes (aspen), the largest stands of which occupy north 

 slopes or old burns, usually above elevations of 7.500 feet. In rocky 

 situations and on north slopes Pseudotsuga taxifoUa (Douglas-fir) may 

 be found at all elevations above 7,000 feet, and pinyon and juniper 

 are frequently found among the pines below that elevation. 



The floor of the pine forests in northern Arizona is sometimes very 

 bare in appearance prior to the summer rains, but under virgin con- 

 ditions bore a light or heavy cover of perennial grasses, in addition to 

 scattered shrubs, perennial composites, and smaller root perennials. 

 The commonest and most widespread of the grasses are Festuca 

 arhonica, Muhlenbergia montana, BouteJuua gracilis, Blepharoneuron 

 trieholepis, and Aristida arizonica. Other common grasses are Sporo- 

 bolus interruptux, Agropyron smithii, MvMenbergia rigens, Bromus 

 cUiaius, MvMenbergia richardsoniSj and M. wrighiii. 



Among the herbaceous perennials of common occurrence in the pine 

 forests of northern Arizona may be mentioned: Iris missouru 

 Comandra pallida, Eriogonum alatum, E. racemosum, Silem laciniata, 

 Poterdilla thurberi, Lupinus spp., Trifolium fendleri, Psoralea tenui- 

 flora, Dalea albiflora, Oxytropis lambertii, Lathyrus spp.. Cologania 

 longifolia, Phaseolus angustissimus, Gayophytum ramosissimum, Frasera 

 speciosa, Asclepwdora decumbens, Gilia aggregata, Phacelia heterophyUa, 

 Monarda mtnthaefulia, Penstemon barbatu*, P. linarioides^ P. virgatus, 



