Mistletoe in the Southwest. 245 



The variety viUostim attains probably its most general dis- 

 tribution on Ouercus arizonica, having been seen frequently on 

 this widely prevalent host in at least six or seven mountain 

 ranges. It is also common on the blue oak {Q. oblonqifolia) , of 

 lesser altitudinal range, being noted from the Catalinas, Rincons, 

 Dragoons, and of frequent occurrence in many parts of the Chiri- 

 cahuas and Oro Blancos. In the threelast-namedrangesitafifects 

 also theToumey oak, usuallv in the i orm of the variety orbiculaf am. 

 On the wliole it is decided! \ infrequent on Ouercus Emoryi, 

 having been noted but rarelv in the Chiricahuas and Catalinas, 

 and not at all in the Oro Blancos and Rincons. Rather ano-nal- 

 ously, it was foimd abundant on ir.any trees in the Santa Ritas 

 near Rosemont. It has been recorded once only on().n'/yci</(i/a, 

 viz., a tree in .Shake Gulch of the Chiricahuas. This rarity may 

 be due to the high range and usual shrubby character of this oak. 

 It has never been seen to affect the widely prevalent (J. hypoleuca. 



Phoradendron calijornicum was first seen between Benson 

 and Mescal, on mesquite, and on the Pantano Wash at Vail on 

 Acacia Gregqii. Subsequently it was noted on one or both of 

 these hosts on the San Pedro River, Baboconieri Creek, in the 

 Roskruge Range, the Altar \'alley, and a large number of desert 

 washes, ranches, and other localities in southern Arizona as 

 well as across the boundary in Sonora. It is especially heavy on 

 acacia on lower Arivaca Creek, occurs on the same and on palo 

 verde (Cercidium Torreyanum) near the Roskruge Range on 

 the latter host near Palo Alto, and is conspicuous and abundant, 

 on this host as well as on Prosopisrelutina and Parkinxoniamicro- 

 phylla on comparatively well watered portions of the bolson plain 

 sloping northward from the Sierritas. 



It may be helpful, finally, to give somewhat more detailed 

 occurrences in the vicinity of the Desert Laboratory domain. 

 Within the tract itself the parasite occurs upon Prosopis, not in- 

 frequent! v upon Parkinsonia microphylla, and near the sinnmit 

 of Tumamoc Hill it has been located upon a bush of Acacia 

 constricta. Later it was noted several times upon the same host 

 below the Pueblo Mine, and at the head of Tumamoc Wash in the 

 Tucson Range, where it likewise occurs upon the other Acacia, 

 upon Cercidium, Parkinsonia, and Condalia spathulata. The first 

 note of its occurrence upon the last named host, 

 like Acacia constricta exclusively shrubby, was made some 



