88 MISSOURI BOTANICAL GARDEN. 



cluster longer, jointed near the base; valves 2 to 3x4 to 5 

 mm., triangular ovate, acute, more delicately veined; cal- 

 losities variable in number, smooth or mostly pitted, often 

 nearly as long as the valve, 1 mm. or more broad, leaving 

 typically a very narrow margin on each side; achene 

 1.3 x 1.7 to 2.5 mm. Floral 1821, 28; Meisner, DC. 

 Prod. xiv. 47. Arctic "America across to Alaska, south to 

 New Hampshire, the Great Lakes, and in the mountains to 

 Southern California and Mexico, where it closely approaches 

 fi. Mexicanus. Specimens examined from various British 

 American points between New Brunswick and Vancouver 

 Island; Alaska (Tiling, 1867, 394); and Maine (Boott, 

 1861; Band, 1888), New Hampshire (Canby, 1866), 

 Ashland, Wisconsin (Farwell, 1887), Keweenaw Co., Mich. 

 (Farwell, 1890), Western Missouri! (Bush, 1890), Wash- 

 ington, Oregon (Hall, 1871, 441; Lyall, 1858, 1860; 

 Howell, 1882), California, Montana (Scribner, 1883, 246), 

 Idaho, Wyoming (Forwood, 1882, 177), Colorado, Utah 

 (Ward, 1875, 540; Palmer, 1877, 421), New Mexico 

 (Fendler, 1847, 760 and 761; Rusby, 1880), Arizona 

 ( Coues and Palmer, 1865), Nevada ( Watson, 1868, 1051), 

 Texas (Merrill, 1886), and Lower California (Orcutt, 

 1884). Plate 26. 



As here accepted, this species comprises several forms so 

 far as the fruiting valves and achenia are concerned. The 

 Asiatic form is said to have only one or two of the valves 

 with callosity. In this respect two principal American 

 forms may be distinguished: a, with valves deltoid or 

 abruptly acuminate, often evidently denticulate below, the 

 margin conspicuous on either side of the frequently solitary 

 callosity; b, with valves more narrowly triangular, nearly 

 or quite entire, nearly concealed by the mostly 3 large 

 callosities. The first in its more toothed form is var. 

 denticulatus,Torr. Bot. Mex. Bound. (1859), 178. The 

 second in its most pronounced form is var. angustifolius, 

 Ledebour, Fl. Ross. iii. (1849), 504. It may be that 

 these forms will bear separation, even from the Old World 

 type; but the (frequently young) specimens in herbaria 



