LACTUCA IN IOWA 243 



garding their distribution and frequency. lie also states that 

 hybrids between this and the common garden lettuce have been re- 

 ported. 



This species was introduced into Iowa about ten years earlier than 

 L. scar'wla, but throughout the central and southern parts of the 

 state the latter seems to be getting the stronger foothold. L. virosa 

 is the prevailing form in the arid regions of the west, its foliage 

 being better calculated to resist the arid conditions. 



Specimens examined : 



lozva: Ames, Pammel, 1897, 1904, 1911, 1912, 1913; Campbell, 

 1909, 3 sheets; Ellis, 1914; McKinncy, 1916; Harlan; Okoboji, 

 Cratty, 1901; Burlington, Pammel, 1918; Council Blufifs, Pammel, 

 1918; Des Moines, Bakke, 1912; Paimiiel, 1894. 2 sheets; Kddyvillc, 

 Pammel, 1912; Decatur County, Anderson, 1914; Eagle Grove. 

 Pauuncl, 1894; Marshalltown, Pammel, 1902; Winneshiek County, 

 Goddard, 1895; Herbarium, T. J. l'it.zpatrick\ Henry County. 1895. 

 Van Buren County, 1896, Dubuque County, 1895, Fremont County, 

 1898, Taylor County, 1898, Johnson County, 1896; Herb. Iowa 

 State University, Coll. B. SJiimek, Hamburg, 1898, Jackson County, 

 1894, Keokuk, 1895, Forest City, 1895, Dallas County, 1897, Rock 

 Rapids, 1896, Davenport, 1895, Spirif Lake, 1896, Clear Lake, 1890; 

 Jasper County, Miss Cavenaiigh, 1898; Muscatine, Ferd. Reppert, 

 1896; Kossuth, Cratty, 1896; Goldl^eld, Cratty, 1896; West Bend, 

 Cratty, 1919; Madison County, Pammel, 1919. 



North America : Michigan — Dearborn, Stezvart, 1898. Illinois — 

 LaSalle, Pammel, 1918; Champaign, Fink, 1892; Urbana, Trelease, 

 1916. Wisconsin— U.7i<\\son, Allen, 1914, 4 sheets; Churchill, 1893: 

 "Wisconsin" Herb. Parry. OA/o— Mansfield, Wilkenson, 1896. 

 Missouri — Kansas City, Pauuncl, 1918. Montana — Billings, Pam- 

 mel, 1904, 2 sheets. Colorado — Greeley, Pammel, 1901 ; La Porte 

 Pammel & Johnson, 1901 ; College Farm, 1898. Utah — Logan, Isa- 

 bel Mulford, 1896. lVashington—SQ^ii\Q, Pammel 1906. 



2. Lactuca scariola L. sp. PI. Ed. 2. 1119 (1763), Prickly Lettuce. 



Similar to the preceding species in flowers and fruit, but leaves 

 pinnatifid, with spinulose-denticulate margins, one edge of the leaf 

 usually inclined upwards. Although given specific rank here it 

 might possibly be better considered as a variety of the former. Al- 

 though appearing in the state some years later than L. virosa it is 

 spreading very rapidly and promises to be the most troublesome 

 of the two. 



