Let (G, K) be a classical symmetric pair defined by the involution a o
n G. Let (g, f) be the corresponding Lie algebras. Given a theta-stabl
e Borel subalgebra b we determine a dense K-orbit in K.(b (perpendicul
ar to) boolean AND i (perpendicular to)). In the case when (G, K) is o
f type AIII or BDI, we use this information to compute the harmonic po
lynomial determined by the associated cycle of a large discrete series
representation. (C) 1998 Academic Press.