98 Muhlenbergia, Volume 8 



the Chiricahiias by E. cremilata. They grow under very simi- 

 lar conditions in the same zone, and show the same biological 

 form, yet they are apparently specifically distinct, indicating 

 development along different lines. Among the Chiiicahua spe- 

 cies are E. crenulata^ E. dentata and several related forms, E. 

 bilobata^ E. exstipidata, E. stictospar^ and E. serpens. Of these 

 only E. bilobata was recollected near Nogales, and of the Tuc- 

 son species, E. Preslii. Nineteen numbers from Tucson and 

 the surrounding mountains were sent in February, 1910, to Dr. 

 C. F. Millspaiigh, of the Field Museum, who very courteously 

 made the determinations as herewith given. 



Euphorbia versicolor Greene, Bot. Gaz 6: 184. i88r. 

 Desert Laboratory, Tucson, Arizona, September 7, 1908, 

 no. 2j0^^ Growiug near a recent earthdnmp, and also along the 

 road to the laboratory. It is a small, prostrate, hairy annual, 

 the flowers with a dark center and foliage of a handsome, red- 

 dish color. Its habitat and scarcity point to recent introduction. 



Euphorbia setiloba Engelm. Pac. R. R. Rep. 5: 364. 1857. 

 Tucson, September 19, 1908, no. 2^o_^. This hairy, creep- 

 ing annual with minute leav^es, resembles E. versicolor^ but its 

 corolla lobes are irregularly toothed. It is found on the sands 

 of Tummamoc wash, where it is abundant, varying much in 

 size, flowering plants often being very small. 



Euphorbia albomarginata T. & G. Pac. R. R. Rep. 2: 174. 



1855- 

 On the rich soil of the flood bottoms of the Santa Cruz 

 river at Tucson, September 30, 1908, no. 2^^o6. Closely creep- 

 ing, its long runners or branches often gracefully .serpentine. 

 The rather large corollas, and many of its leaves turning red at 

 this season, together with its graceful habit, makes it an attrac- 

 tive plant. Also seen in the yard of St. Mary's ho.spital, and on 

 Tummamoc wash. 



Euphorbia prostrata Ait. Hort. Kew. ed. i. **: 139. 1789. 

 On the Santa Cruz river bottom at Tucson, September 25, 

 1908, no. 2c;oj. Creeping in dense mats on silled outwash, 



