THE GENUS LACTUCA IN IOWA. 



R. I. CRATTY. 



The present paper on the genus Lactuca and its distribution in 

 Iowa is the resuh of a study of this group of plants carried on at 

 the Iowa State College during the past two years, supplemented by 

 field work, and a visit to some of the other large herbaria in the 

 state. The extensive collection of this genus in the State College 

 herbarium, very largely the result of Doctor Pammel's work, has 

 been freely used. To Dr. B. Shimek the author is indebted for the 

 privilege of examining the Lactnccc in the herbarium of the State 

 University, and to Prof. T. J. Fitzpatrick, of the State University 

 of Nebraska, for access to his fine herbarium near Iowa City, which 

 contains an especially rich and valuable collection of Iowa plants. 

 The Hon. O. M. Oleson, of Fort Dodge, kindly loaned some speci- 

 mens for examination. Mr. C. Neuberth, of the Field Columbian 

 Museum, Chicago, also granted access to the Lactuca: in that insti- 

 tution. To all these gentlemen grateful thanks are extended. For 

 the drawings of the akenes in the plate accompanying this paper 

 the writer is indebted to Miss Charlotte M. King, of the Iowa State 

 College, whose skillful hand has done so much to illustrate the nu- 

 merous publications issued by this institution. 



Some of the species of Lactuca are very puzzling, especially when 

 only leaves and flowers are present, on account of the great varia- 

 tion in the color of the flowers, and the greater diversity of leaf 

 forms in several species. The mature fruit should be secured if 

 possible, as it is a great help in determination. 



The genus Lactuca is represented in our state flora by eight spe- 

 cies, six of which are native. It belongs to the subfamily Cichoria- 

 cecc of the great family Compositcc. The genus Mulgedium is con- 

 sidered distinct by Engler and Prantl in Die Naturlischcn Pflanzcn- 

 familicn, and by DeCandolle in the Prodromus, but by Bentham and 

 Hooker it is reduced to a section of Lactuca and in this they are fol-' 

 lowed by most American botanists. , 



There is a great diversity of opinion among our systematists re- 

 garding the disposition of the Linnaean species L. virosa and L. 

 scariola. The oldest described species of this group is L. virosa ^nd 



