Dr. Jeffrey M. Osborn
Dean of the School of Science and Professor of Biology
The College of New Jersey
Osborn, J. M., T. N. Taylor, and E. L. Schneider. 1991. Pollen morphology and ultrastructure of the
Cabombaceae: Correlations with pollination biology.
American Journal of Botany 78: 1367-1378.
Of all species comprising the two genera of the Cabombaceae, only Brasenia schreberi J. F. Gmel. and
caroliniana Gray have been critically investigated with regard to their pollination biology.
has been shown to be anemophilous, while C. caroliniana has an entomophilous (myophilous) pollination syndrome.
In the present paper, a number of pollen and pollen-related characters, including pollen size, shape, quantity,
terminal settling velocity, pollen-ovule ratios, and overall exine architecture of B.
schreberi and C. caroliniana
are evaluated. Pollen from both species is elliptic, monosulcate, and has a tectate-columellate sporoderm with
supratectal surface ornamentation. Grains of B. schreberi are small, produced in copious amounts, and settle
relatively slowly. Flowers of this species have large pollen-ovule ratios. The exine of B.
is scabrate, relatively thin, has a uniformly thick sexine, composed of a two-zoned (homogeneous/granular) tectum
and distinct columellae, and a homogeneous nexine. Pollen of C. caroliniana is relatively large, produced in small
quantities, and has a rapid terminal settling velocity. Flowers exhibit small pollen-ovule ratios. Exine
organization of C. caroliniana pollen is typically two times thicker than that of B.
is striate. Nonapertural sexine regions have a thick tectum and well-defined columellae, with both sexine
components traversed by a dense system of channels. The nexine is relatively thin. All of the palynological
characters examined correlate well with the anemophilous and entomophilous syndromes of B. schreberi and
C. caroliniana, respectively. Moreover, several other parameters of exine ultrastructure from each species exhibit
positive correlations with the respective pollination mechanisms, these include: tectum thickness, columellae
diameter, tectum-nexine ratios, and the consistency/distribution and total amount of pollenkitt present. Overall
exine ultrastructure is also discussed from an historical perspective as well as with respect to its phylogenetic
Brasenia, Cabomba, pollen, morphology, ultrastructure, pollination,
anemophily, wind pollination, myophily, fly pollination.