PIPER FLORA OF THE STATE OF WASHINGTON. 551 



Range: Washington, Oregon, Missouri, Tennessee. 



Specimens examined: White Salmon, SwArsdor/" 189; Wawawai, Piper 1593. 



Zonal distribution : Humid Transition. 



3. Xanthium oligacanthum sp. nov. 



Stem erect or spreading, 30 to 60 cm. high, sparsely hispid; leaves reniform-orbicular, 

 obscurely lobed and crenate, harshly scabrous, hispid on both faces, the petioles as long 

 or longer than the blades; fruiting involucres oblong, the body 1.5 cm. long, 5 to 7 mm. 

 thick, the stout beaks somewhat incurved; prickles 15 to 25, uncinate-tipped, about as 

 long as the diameter of the fruit ; surface of the fruit and base of prickles pubescent. 



Bolles, Walla Walla County, Piper, September 18, 1893; also found at Waitsburg by 

 Homer (no. B 272). The type is in the National Herbarium. This differs from any other 

 American species in the small size of the fruit and the relatively few prickles. 



4. Xanthium af9.ne Greene, Pittonia 4: 60. 1899. 



Type locality: " Sandy banks of the Columbia River, Klickitat County, Washington." 

 Collected by Suksdorf. 



Range: Washington., 



Specimens examined: West Klickitat County, SuTcsdorf 1583; Spokane, Kreager 537; 

 Piper September 1, 1899. 



5. Xanthium varians Greene, Pittonia 4: 59. 1899. • 



Type locality: "Sandy banks of the Columbia River, Klickitat County, Washington." 

 Collected by Suksdorf. 

 Range: Washington. 

 Specimens examined: West Klickitat County, /SwitstZor/" 1583; Waitsburg, Homer 27S'B. 



Xanthium echinatum Murr. and Xanthium steumakium L. are names which appear 

 in Suksdorf 's list, but they are erroneous determinations of some of the above species. 



AMBBOSIA. Ragweed. 



Leaves all opposite; receptacle without chaff 1. A. trifida. 



Leaves opposite and alternate ; receptacle chaffy. 



Fruiting involucre spiny; leaves thin 2. A. artemisiaefolia. 



Fruiting involucre tubercled; leaves thick 3. A. psilostachya. 



1. Ambrosia trifida L. Sp. PI. 2: 987. 17.53. 

 Type locality: " In Virginia, Canada." 



Range: Saskatchewan and Canada to Texas and Florida. 



Specimens examined: Walla Walla, Piper, August 13, 1897 (introduced). 



2. Ambrosia artemisiaefolia ii. Sp. PI. 2: 988. 1753. 

 Type locality: " Habitat in Virginia; Pennsylvania." 

 Range : British Columbia to Nova Scotia, south to Texas. 



Specimens examined: Mission, Kreager 495. ♦ 



2a. Ambrosia artemisiaefolia diversifoha subsp. nov. 



Leaves becoming progressively less deeply lobed upward, those of the upper third of 

 the plant mostly entire, these ovate-lanceolate or lanceolate, acute, narrowed abruptly 

 to a subsessile base, 3-nerved. 



On the gravelly banks of Almota Creek at Alraota, Piper, August 26, 1894 (no. 1837). 

 At this place it seems unquestionably to be native. The entire or subentire upper leaves 

 present a peculiar characteristic which does not seem to be approached in any eastern 

 specimens. The plant may represent a distinct species, but in the absence of more abun- 

 dant material it seems best to treat it as above. 



The typfe is in the National Herbarium. 



