1905] Dewey,— Identity of Prickly Lettuce II 
Canada was in press at the time the specimen from Ohio was being 
studied. Attention was called to the misidentification of the plant, 
and Lactuca virosa was inserted in the appendix. 
Since then the writer has examined several specimens from the 
Gray Herbarium and all of the Lactucas in the Herbarium of the 
Missouri Botanic Garden, and also in the Herbarium of the Field 
Columbian Museum as well as the U. S. National Herbarium. 
These collections include several European specimens of both Z. vi- 
rosa and L. scariola, the correct identification of which is not to be 
doubted. These two species are abundantly distinct, but our com- 
mon prickly lettuce does not agree with typical forms of either species. 
There was one specimen from the Gray Herbarium agreeing per- 
fectly with our common form with merely dentate leaves, and labeled 
Z. scariola integrata, Gren. et Godr. A further study of specimens and 
descriptions seems to prove that this is the correct solution of the three- 
cornered puzzle. ‘The common prickly lettuce, having leaves without 
lobes, is Z. scariola integrata, Gren. et Godr. Fl. France, 2: 320, 18 50. 
The true Zactuca scariola is rare in this country, except in the 
central Ohio valley and Zactuca virosa is not found here at all. 
The original description of Zactuca virosa in Linnaeus Species 
Plantarum ! included also Z. scario/a and two illustrations are referred 
to in Morrison's Historia. One of these figures shows a plant with 
merely dentate leaves and tbe other with lobed leaves. Three years 
later Linnaeus published in Centuria II? his discription of Z. 
scariola referring to the figure with lobed leaves in Morrison's His- 
toria, and furthermore stating that Z. scariola “differs from Zactuca 
virosa (from which it is to be distinguished) in the vertical not hori- 
zontal plane of its leaves." The leaves of both forms in this country 
are turned in a vertical plane, and also to the north and south, when 
the plants grow in the open so that they are exposed to the light. 
The true Zactuca scariola has been collected on ballast at New 
York, on the site of an Italian railway construction camp in Wash- 
ington, and in Ohio, Indiana and Kentucky it is abundant within 
a hundred miles of Cincinnati. In Washington it does not spread, 
although the variety ¿ntegrata is an aggressive weed there. 
Aside from the leaves there seem to be no characters distinguish- 
ing the species from the variety, and a few specimens among the 
1 Sp. Pl. 795 (1753). 
* Centuria II (1756). Reprinted in Amoen. Acad. 4: 328 (1759). 
