KANTZ, KATHERINE E.* AND SHIRLEY C. TUCKER. Biology Dept., Grand Valley State University, Allendale, MI 49401 and Dept. of Biology (Ecology, Evolution and Marine Biology), University of California, Santa Barbara, CA 93110. - Floral development of Chrysobalanus icaco L. and Licania michauxii Prance (Chrysobalanaceae): stamen number and formation of the gynobasic style.
Members of the Chrysobalanaceae are distinguished by a single pistil
with a gynobasic style. The purpose of this study was to examine the
floral development of representatives of this family in order to
determine how the gynobasic style is formed. The flowers of the two
representatives examined, Chrysobalanus icaco and Licania
michauxii, also differ in the number of stamens they typically
have (12-26 in C. icaco and approximately 15 for L.
michauxii). The pattern of stamen development was therefore also
examined to determine how this difference in number is achieved. The
difference in the number of stamens between the two species was found
to be due to two processes: a larger number of stamens being initiated
in the inner whorl of C. icaco flowers (typically four opposite
each petal as opposed to two opposite each petal) and subsequent
suppression of stamens on one side of the C. icaco flowers.
Carpel initiation in L. michauxii begins when three carpel
primordia become visible during initiation of the antepetalous stamen
whorl. The originally distinct carpel primordia become laterally
confluent in the portions below the free tips. Later in development
the ovaries of two of the carpels are suppressed leaving a single
developing ovary. The developing ovary expands outward and upward
causing the style, which is apparently composed of tissue from all
three carpels, to become gynobasic. Only two carpel primordia are
initiated in flowers of C. icaco. Further development of the
gynoecium is similar to that found in L. michauxii in that one
of the two ovaries is suppressed leaving a single developing ovary
with a gynobasic style apparently composed of tissue from both
carpels. In conclusion the gynobasic style is produced by a
suppression of ovaries in both species, although different numbers of
carpels are initiated and suppressed in the two species.
Key words: Chrysobalanaceae, Chrysobalanus icaco, floral development, gynobasic style, Licania michauxii