standley: floras of new Mexico and Argentina 241 



we have but a single one. Strombocarpa strombalifera is in many 

 respects similar to S. pubescens, the well-known screw-pod mes- 

 quite or tornillo of the Southwest, especially in its fruits, which are 

 almost identical. But the Argentine plant can scarcely, like its 

 New Mexican ally, be an important source of firewood, for it is 

 only two or three decimeters high. 



Besides the instances just mentioned, certain Argentine species 

 of Persicaria, Gutierrezia, Grindelia, Astragalus, Clycyrrhiza, Le- 

 pidium, Pappophorum, Monnina, Phacelia, Polygala, Ximenesia, 

 Senecio, Disiichlis, Stipa, Poa, Sophia, and Heliotropium bear a 

 general resemblance to New Mexican species of the same genera. 

 There are also represented in the collection such genera as Myri- 

 ophyllum, Tissa, Allocarya, Amsinckia, Bowlesia, Pectocarya, Bud- 

 dleia, and Hydrocotyle, which are not represented in the Mesilla 

 Valley, although they occur in regions not far distant. Most of 

 these genera, also, consist in the United States of characteris- 

 tically southwestern plants. It is significant to find about Rio 

 Negro a curious xerophytic shrub belonging to the Caper Family, 

 Atamisquea emarginata Miers, a species found also in Lower Cali- 

 fornia but unknown in the intervening countries. Several genera 

 which occur in the Southwest are represented in Argentina by 

 species very unlike the North American ones. Some of these are 

 Lippia, Elymus, Frankenia, Verbena, Menodora, Prosopis, Atri- 

 plex, Sida, Eupatorium, Eryngium, and Sporobolus. The Ver- 

 benas are specially interesting; species of this genus are very 

 numerous in southern South America, but many of them are strik- 

 ingly different from our North American ones, all of which fall 

 into two groups, each composed of similar plants. Some of those 

 of Argentina are shrubs, often with curious leaf form, and some 

 of them have yellow flowers. 



Of course, there are represented in this Argentine locality 

 genera of which no species are found in the southwestern United 

 States. Among them are Mulinum and Asteriscium (Apiaceae), 

 Chuquiragua and Cyclolepis (Mutisiaceae), Adesmia (Fabaceae), 

 Fabiana and Treclionaetes (Solanaceae), Facelis and Hysterionica 

 (Asteraceae) ,♦ Turrigera and Oxystelma (Asclepiadaceae) , Schinus 



