Lactuca serriola (Prickly Lettuce) has been added to my Wildflowers of Tucson, Arizona website.

This lanky, pale yellow-flowered, European and Mediterranean weed is closely related to cultivated Garden Lettuce, and genetic studies have indicated that Prickly Lettuce is likely the ancient ancestor of all the many cultivars of Garden Lettuce. After selective cultivation countless centuries ago, Garden Lettuce no longer has Prickly Lettuce's erect form, white latex sap, bitterness, and spiny lower midribs.