XIV. STUDIES IN THE GENUS LACTUCA IN WESTERN 

 PENNSYLVANIA. 



By O. E. Jennings. 

 (Plate XXXIII.) 



During seventeen years of l)otanizing in the region of Pittsburgh 

 the writer has been annually impressed with certain peculiar char- 

 acteristics of some of the species of Lactnca occurring here. Various 

 collections and very numerous observations in the field have served 

 to confirm the suspicion that certain of the species, as they occur in 

 this region, possess characteristics in part dififerent from the typical 

 forms of the species as described in current botanical literature. To 

 render the identification of the local forms more exact, and thus to 

 aid in better establishing their geographical limits, the new varieties 

 herein named are proposed. 



Lactuca spicata variety aurea var. nov. 



There grows abundantly in uncultivated grounds and neglected lots 

 and fields throughout Allegheny and adjacent counties a tall Lactnca 

 with tawny or sordid pappus, which generally agrees quite well with 

 Lactnca spicata (Lamarck) Hitchcock, except that the plant is more 

 robust and the flowers are bright lemon-yellow, often withering to 

 bright orange. Among thousands of the plants observed in various 

 parts of the region all had yellow flowers, with the single exception 

 of a plant with very light-colored flowers, suggesting albinism. 



As first described, in Lamarck's Encyclopedic, in 1789, Sonchus 

 spicatus from South Carolina had purplish flowers {" Les fleiirs sont 

 purpurines"),'^ and in DeCandoUe's Prodromus, in 1838, Section II, 

 under Agalma of the genus Mnlgedhnn, it was characterized as 

 follows: "Pappus sordcsccns. Iirrol. calyciilafinn ant calyculato-im- 

 hricatum. Cor. ca-rulccc aiit purpurccc." And under this section was 



1 Lamarck, J. B. A. P. M., Encyclopedic Methodique, Botanique, III. 1789, 

 p. 401. 



440 



