In order to pin a more complete understanding of the organization of t
he mitotic apparatus (MA) in the generative cells (GCs) of flowering p
lants, pollen tubes of Nicotiana tabacum were examined using tubulin i
mmunocytochemistry and Hoechst fluorescence. The observations were the
n compared with previously published information on Tradescantia GCs a
nd the MA of somatic cells. At the onset of division, the prominent mi
crotubule (Mt) bundles characteristic of GCs are reorganized into a mo
re random Mt network. At late prophase/prometaphase, kinetochores appe
ar to interact with this network, resulting in the formation of K-fibe
rs that frequently link in tree-like aggregates. The GC MA takes the f
orm of a distinct spindle and often has pointed, focused poles; the me
taphase plate is usually oblique. Karyokinesis involves both anaphase
A and B; lengthening of interzonal Mts is accompanied by elongation of
the spindle. In late anaphase/early telophase, phragmoplast Mts are f
ormed in association with the proximal face of the sperm nuclei. The p
hragmoplast remains prominent for some time, so that its Mts as well a
s another population generated from the distal face of the sperm nucle
i constitute the initial sperm cytoskeleton. Comparisons indicate that
the spindle in tobacco GCs falls on a continuum of organization betwe
en that of somatic cells and the MA of Tradescantia GCs.