Cos lettuce (var. longifolia Lam., var. romana Hort. in Bailey) (Römischer Salat, Laitue romaine) Plants with tall loose heads, which are sometimes tied up; oblong rigid leaves with a prominent midrib running almost to the apex, are eaten raw or cooked. The name of the morphotype is taken from the Greek island Cos (Kos), where the type has long been cultivated. Cos lettuce is most common in the Mediterranean countries of Europe, Western Asia and North Africa (Ryder 1986). According to Boukema et al. (1990), many landraces of this type maintained at the CGN genebank collection originated mainly from Egypt, Iran, Turkey and Syria.

On doit la Grasse de Morges au travail de sélection de la maison Tschirren à Morges en 1930. Et depuis les années 80, c’est la Station de Recherches Agronomique de Changins qui assurait la conservation de la variété.