Ultrastructure of spermatium ontogeny in Puccinia coronata avenae

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Abstract
Spermatium formation in Puccinia coronata avenae was concluded to be annellidic but with some phialidic analogies. The spermatiophore wall consisted of a prominent outer layer and a very thin inner layer. During formation of the first spermatium initial, the apical end of the spermatiophore became somewhat swollen and a septum was then formed centripetally at the base of the swelling to delimit the primary spermatium. The wall layers of the first spermatium were derived from the wall layers of the spermatiophore. The mature septum consisted of two bilayered walls separated by a clear septal lamella. The upper septal wall formed the basal wall portion of the preceding spermatium and the lower septal wall became the distal wall portion of the succeeding spermatium. The layers of each septal wall were confluent with the inner and outer periclinal wall layers of the developing spermatia. After spermatium secession, the broken outer wall layer left remnants as a basal frill on the spermatium and an annular scar on the spermatiophore. Each succeeding spermatium formed at a near-fixed locus on the spermatiophore. Although the formation of succeeding spermatia appeared superficially to be phialidic, examination of wall relationships indicated that the formation of each successive spermatium recapitulated the holoblastic first spermatium.As the spermatia matured, the outer wall layer, including the basal frill, gradually dissipated. The thickness of the spermatium wall was maintained by expansion of the inner layer. In mature spermatia, the inner layer comprised the bulk of the wall, and the outer layer was left as a thin tenuous band surrounding the spermatium.