PIPER—FLORA OF THE STATE OF WASHINGTON. 551 
Rance: Washington, Oregon, Missouri, Tennessee. 
SPECIMENS EXAMINED: White Salmon, Suksdorf 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 
Horner (no. B 272). The type isin the National Herbarium, This differs from any other 
American species in the small size of the fruit and the relatively few prickles. 
4. Xanthium affine Greene, Pittonia 4: 60. 1899. 
Type Locauiry: ‘Sandy banks of the Columbia River, Klickitat County, Washington.” 
Collected by Suksdorf. 
Rance: Washington. 
SPECIMENS EXAMINED: West Klickitat County, Suksdorf 1583; Spokane, Areager 537; 
Piper September 1, 1899. 
5. Xunthium varians Greene, Pittonia 4: 59. 1899. 
Type Locauity: ‘‘Sandy banks of the Columbia River, Klickitat County, Washington.” 
Collected by Suksdorf. , 
Rance: Washington. 
SPECIMENS EXAMINED: West Klickitat County, Suksdorf 1583; Waitsburg, Horner 273 B. 
XaNnrTHIUM ECHINATUM Murr. and Xanruium struMArtuM L. are names which appear 
in Suksdort’s list, but they are erroneous determinations of some of the above species. 
AMBROSIA. RaGweep. 
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. Pl. 2: 987. 1753. 
Type Locauity: ‘‘ In Virginia, Canada.”’ 
Rance: Saskatchewan and Canada to Texas and Florida. 
SPECIMENS EXAMINED: Walla Walla, Piper, August 13, 1897 (introduced). 
2. Ambrosia artemisiaefolia L. Sp. Pl. 2: 988. 1753. 
Type Locauity; “ Habitat in Virginia; Pennsylvania.” 
Rance: British Columbia to Nova Scotia, south to Texas. 
SPECIMENS EXAMINED: Mission, Kreager 495. 
2a. Ambrosia artemisiaefolia diversifolia 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 Almota, 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 type is in the National Herbarium. 
