FLORAL DEVELOPMENT OF DIOECIOUS SPECIES AND TRENDS OF FLORAL EVOLUTION IN PIPER SENSU-LATO

The initiation of the floral parts (mainly stamens and carpels) is des cribed for the four dioecious species of Piper: Piper polysyphorum C. DC., P. bavinum C. DC., P. pedicellatum C. DC., P. pubicatulum C. DC. The initiation order resembles that in the perfect flowers of some spe cies, such as P. amalago. The carpels are initiated simultaneously, in most cases: as three primordia. In P. polysyphorum, carpel tips split into two lobes, so that finally a four- or five-lobed stigma will be formed when the ovary is fully developed. The staminodes (exactly, sta minodial primordia) in the female flowers are initiated in the same or der as the stamens in the male flowers and remain until the ovaries ar e enclosed. The unisexual flowers have stamens reduced to three or two . The reduction of stamen or staminode (staminodial primordium) number is accompanied by the change of their positions from opposite the car pels to alternate. After the initiation of the staminodes, or, exactly staminodial primordia, in the female flowers, the central part of the floral apex forms a ring meristem which is triangular. The carpel pri mordia (often three) are initiated on the three points of the ring mer istem. The evolutionary trends of the flowers of Piper sensu lato are discussed. (C) 1998 The Linnean Society of London.