Prior to attachment of the adhesive disk, epidermal cells of the
stem develop into a secretory epithelium of unicellular trichomes which
upon attachment produce finger-like projections from the apical end
in Cuscuta reflexa Roxb, and Cassytha pubescens
R.Br. Viscum minimum Harvey, develops an epithelium of uni- or
bicellular trichomes with blunt tips from the apex of the radicle. The
development of epithelial trichomes and the ultrastructure, development,
disintegration, and partial reorganization of the cuticular membrane
of these secretory cells have been investigated before and after attachment
to the host. On young epithelial cells the cuticular membrane is composed
of a cuticle proper with alternating electron dense and electron translucent
lamellae and a cuticular layer of the reticulate type. Pockets of granular
and fibrillar secretory products are located within the lamellar system
of C. pubescens and V. minimum. Cutin cystoliths occur
most frequently in V. minimum. In all three species the lamellar
system and most of the cuticular layer break up during secretion and
flow towards the surface of the host as part of the adhesive secrete.
After host contact has been established most of the translucent lamellae
are still intact but reorientated. In V. minimum the secrete is predominantly
cutinaceous according to its positive reaction with Sudan IV and auramin-0.
Although mixed with fragments of the cuticular menbrane the secrete
in the two twining species is PAS-positive and most likely pectinaceous.
V. minimum fills the space between the adhesive disk and the
host with enormous quantities of secrete while Cassytha and Cuscuta
only secrete small quantities, and their finger-like projections fill
the space in question. The cuticular menbrane of three different host
species predominantly showed a reticulate ultrastructure.