HOMEOSIS IN FLORAL DEVELOPMENT OF SANGUINARIA-CANADENSIS AND SPERGULARIA-CANADENSIS MULTIPLEX (PAPAVERACEAE)

Sanguinaria canadensis is a member of the Papaveraceae that normally h as eight petals rather than four as is usual in the family. Using epi- illumination microscopy to study floral development, we show that the four additional petal primordia are initiated in positions that corres pond to the first four''stamen positions in species of the Papaveracea e with four petals. Also, these additional petal primordia share early developmental features with stamen primordia: at inception they are c ircular in outline, and the relationship between organ length and widt h while very young is similar. The developmental pathway of the additi onal petals combines both stamen and petal features: initially stamenl ike in appearance, they develop into typical petals. The additional pe tals of S. canadensis can therefore be interpreted as homeotic because petal features are expressed in stamen positions. Organogenesis in th e 'Multiplex' cultivar is similar to that of its wild progenitor, but during development all primordia in the androecial region become petal s. This cultivar, as well as variants within natural populations, show that replacement of stamens with petals occurs within the species.