VEGETATION OF THE SANTA CATALINA MOUNTAINS. 19 



Ephemeral Summer-active Herbaceous Plants — Continued. 



Root Perennials {all facultative evergreens): 

 *** Abutilon incanum, sclerophyllous. 

 ** Brodioea capitata var. pauciflora, 



bulbous, linear leaves. 

 ** Cassia coyesu,sclerophylIous,branched 

 leaves. 



* Dalea parryi, microphyllous. 



*** Muhlenbergia porteri, semi-scandent. 

 ** Pentstemon wrightii, macrophyllous. 

 ** Perezia wrightii, macrophyllous. 

 ** Verbena ciliata, macrophyllous, hairy. 

 Ephemeral Summer-active Herbaceous Plants: 

 ** Bahia absinthifolia. 

 *** Baileya multiradiata. 

 ** Boerhaavia pterocarpa. 



* Boerhaavia walsoni. 

 *** Bouteloua arislidoides. 

 *** Cladothrix lanuginosa. 



** Euphorbia fiorida. 



* Euphorbia melanadenia. 



Ephemeral Summer-active Herbaceaus Plants: 

 Continued. 

 *** Pedis papposa. 

 *** Wedelia incarnata. 

 Ephemeral Winter-active Herbaceous Plants. 

 ** Actinolepis lanosa. 

 ** Anisololus trispermus. 

 *** Baeria chrysostoma. 

 ** Chorizanthe brevicornu. 

 ** Cryptanthe intermedia. 



* Eremocarya micrantha. 

 *** Gilia floccosa. 



** Lepidium lasiocarpum. 

 ** Lesquerella gordoni. 



* Mentzelia albicaulis. 



* Orthocarpus purpurascens. 

 ** Pectocarya linearis. 



*** Plantago fastigiata. 

 *** Plantago ignota. 



THE DESERT ARROYOS AND CANONS. 



In crossing the Upper Bajadas it is often possible to detect, by means 

 of the vegetation, the approach to a very shallow drainageway through 

 which water runs for only a few hours after the severest summer rains. 

 The larger arroyos are still more conspicuous by reason of the still 

 heavier stand of vegetation along their margins, and in the largest 

 caiions is found the culmination of the influence of surface streams 

 and underflows for the support of vegetation. The effect of the most 

 transitory of the small streams is merely the raising of the moisture of 

 adjacent soil to such a point that it will present favorable conditions 

 for plant activity for a longer time after the close of the rainy periods 

 than will the soil of the bajada in general. There is only a negligible 

 and short-lived underflow in these smallest arroyos, and their only 

 differences from the bajada are that in the rainy seasons they present 

 sHghtly more favorable conditions with respect to soil moisture and 

 that the effect of the rainy season is slightly prolonged in them, while 

 the periods of drought are correspondingly shortened. In the larger 

 arroyos there may not be a constant underflow, but there is at least a 

 relatively high percentage of soil moisture for periods of sufficient length 

 to greatly reduce the influence of the arid periods upon their plants. 

 In the largest arroyos and in the mountain canons themselves there is 

 either a constant underflow, maintaining high moistures in the soil of 

 the banks and bed of the arroyo, or else there is constant water, either 

 running or standing in pools. 



The smallest arroyos, which are very frequent on the Upper Bajada 

 in the close proximity of the mountain, present no peculiar species, but 

 merely a closer stand of the same plants that are to be observed 

 throughout the bajada, notably Prosopis, Acacia greggii, and Momisia 

 pallida. Along somewhat larger arroyos are to be found still heavier 

 stands of the above species, together with Parkinsonia torreyana, Celtis 



