The development of cereal cyst nematode (CCN; Heterodera avenae) induced syncytia in the host roots of infected resistant bread wheat (Triticum aestivum cv. AUS10894), diploid wheat (Aegilops tauschii), barley (Hordeum vulgare cv. Chebec and cv. Galleon) and in the susceptible wheat cv. Meering and barley cv. Clipper were studied over a period of 13 d. The resistance to CCN in these cereal plants is conferred by the resistance genes Cre1 in the wheat cv. AUS10894, Cre3 in A. tauschii, Ha2 in barley cv. Chebec and Ha4 in barley cv. Galleon. Anatomical observations were made on the development of the syncytia in CCN-infected wheat and barley roots, which carry each of these four sources of resistance genes. Accelerated development of the syncytia in resistant plants, especially in the barley cultivars, was observed. The sites of syncytia development in susceptible wheat and barley were also closely associated with the vascular tissues in the stele, but less so in the resistant plants. The syncytia in the infected susceptible wheat and barley were also metabolically active at day 13. By contrast, the syncytia of resistant wheat plants carrying the Cre1 or Cre3 genes remained extensively vacuolated and less metabolically active. In barley plants with the Ha2 or Ha4 genes, the syncytia appeared non-functional and in early stages of degeneration by day 13 after inoculation.

The structure and function of the male accessory reproductive gland system of the cotton stainer, Dysdercus fasciatus Signoret, was studied using ultrastructural techniques. The gland system is composed of a pair of mesadenia and an ejaculatory duct, whose anterior end is swollen and encloses a glandular structure whose origin is not clear. Each mesadene is composed of a large number of sacs whose lumina are confluent. The epithelium of each sac is one cell layer thick and is composed of two cell types, mononucleate and multinucleate cells. The origin and siginficance of the multinucleate condition in the mesadenial epithelial cells is not clear, but it is suggested that this condition might have arisen during maturation, when mitotic divisions are complete, but the nuclei continued to multiply within an increased cytoplasmic mass, which itself does not divide.