632 CONTEIBUTIONS FEOM THE NATIONAL HEEBAEIUM. 



Achenes turgid, ovoid or pear-shaped; bracts of the 



invohicre alike, herbaceous 2. IvA (p. 633). 



Staminate and pistillate flowers in separate heads, the lat- 

 ter 1 to 4, without corollas, inclosed in a nutlike or 

 burlike involucre. 

 Shrub; pistillate involucre with several scarious 



wings 3. Hymenoclea (p. 634). 



Herbs; pistillate involucre not winged. 



Involucres of staminate heads with distinct 

 bracts; pistillate involucres large, with 



hooked spines 4. Xanthium (p. 634). 



Involucres of staminate heads with united bracts; 

 pistillate involucres small, the spines not 

 hooked. 

 Spines or tubercles of the l-flowered pistil- 

 late heads in a single row 5. Ambrosia (p. 635). 



Spines of the 1 to 4-flowered pistillate heads 



in more than one row 6. Gaertnerla. (p. 636). 



1. DICORIA Torr. & Gray. 



Low branched canescent aimuals with alternate petiolate leaves; heads heteroga- 

 mous, of 1 or 2 fertile and several staminate flowers; pistillate flowers without corollas; 

 involucre of 5 short, oval or oblong, herbaceous bracts and 1 or 2 inner enlarged 

 scarious ones; achenes flat on the inner surface, convex on the outer, with dentate or 

 thin and scarious peci-inate edges; pappus rudimentary, of several small scales. 



KEY TO THE SPECIES. 



Achenes 1 in each head; teeth of achenes conspicuous, often con- 

 nected at the base 1. D. brandegei. 



Achenes 2 in each head; teeth of achenes inconspicuous, few, 



distinct 2. D. paniculata. 



1. Dicoria brandegei A. Gray, Proc. Amer. Acad. 11: 76. 1876. 



Type locality: Along the San Juan, between McElmo and Recapture Creeks, 

 Utah. 



Range: Colorado and Utah to northern Arizona and northwestern New Mexico. 



New Mexico: Shiprock {Slandley 7188). Sandy soil in valleys, in the Upper So- 

 noran Zone. 



2. Dicoria paniculata Eastw. Proc. Calif. Acad. II. 6: 298. pi. 45. 1896. 



Type locality: Sandy flats along the San Juan River near the junction with 

 McElmo Creek, Utah. 



Range: Southeastern Utah and northwestern New Mexico. 



New Mexico: Shiprock (Standley 7188a). Sandhills in valleys, in the Upper So- 

 noran Zone. 



The two species were growing together on sandbars along the San Juan at the Ship- 

 rock Agency, and in the field were taken to be the same species. D. paniculata, as 

 stated by Miss Eastwood, blooms earlier than D. brandegei, and the plants collected at 

 Shiprock were in mature fruit and had lost many of their leaves, while those of the 

 latter species were only flowering. 



