ON THE ORIGIN OF CULTIVATED LETTUCE

N connection with cytological and genetical investigations within the I serriola group of Luctuca, results of which have been published in earlier papers (LINDQVIST, 1956(LINDQVIST, , 1958(LINDQVIST, , 1960(LINDQVIST, a, 1960 b) b) , material was obtained of a number of Lactucu forms, the identity of which was at first obscure.They had been given various names, but as the investigations progressed it became clear that they should be considered as primitive types of L. sutiva, although none of them had been received under that name.The purpose of this paper is to provide taxonomic and cytogenetic evidence in support of this opinion and to consider the bearing of the existence of these forms on the theories about the origin of cultivated lettuce.I. TAXONOMY OF THE SERRIOLA SECTION 21 -Heredilns 46 -. 320] I .LINDQVIST cytogenetically, bridge the gap between the serriola group and other species groups.l'he four species of the serriola group may be identified with the aid of the following key:Plant biennial; achenes purplish black, wing-margined, rugose but not spirulate or setose ..........