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Blue-flowered Conospermum species are endemic to Western Australia, and are highly sought after in the horticulture industry. Aspects of the reproductive biology of several species were investigated. The paniculate inflorescences of Conospermum eatoniae E.Pritz. contain 6-10 florets; however, the uppermost two or three florets never open and only the basal one or two florets in an inflorescence set seed. When insect pollinators are excluded, flowers do not self-pollinate and set seed. Stigma receptivity occurred for up to 6 days following triggering of the style and was variable between C. eatoniae, C. amoenum Meisn. subsp. amoenum, C. caeruleum R.Br. and C. brownii Meisn. Hand-pollination with 10 pollen genotypes and two maternal C. eatoniae parents showed that although pollen tubes were observed in the style, no seed was set. Genetic analysis of open-set seed progeny showed that C. eatoniae outcrossed infrequently when grown in clonal rows in a plantation, but outcrossing was common in wild plants. This study demonstrates that the reproductive biology of blue-flowered Conospermum is complex and requires further investigation if the species are to be widely cultivated for horticulture.

Background and Aims: An unusual form of pollen tube growth was observed for several Conospermum species (family Proteaceae). The rate of pollen tube growth, the number of tubes to emerge and the ultrastructure of these tubes are given here. • Methods: Pollen was germinated in vitro in different sucrose concentrations and in the presence of calcium channel blockers, and tube emergence and growth were recorded on a VCR. Measurements were taken of the number of tubes to emerge and rate of tube emergence. Pollen behaviour in vivo was also observed. The ultrastructure of germinated and ungerminated pollen was observed using TEM. • Key Results: After 10 s to 3 min in germination medium, up to three pollen tubes emerged and grew at rates of up to 55 μm s -1; the rate then slowed to around 2 μm s -1, 30 s after the initial growth spurt. Tubes were observed to grow in pulses, and the pulsed growth continued in the presence of calcium channel blockers. Optimal sugar concentration for pollen germination was 300 g L -1, in which up to 81 % of pollen grains showed fast germination. Germination and emergence of multiple tubes were observed in sucrose concentrations of 100-800 g L -1. The vegetative and generative nuclei moved into one of the tubes. Multiple tubes from a single grain were observed on the stigma. Under light microscopy, the cytoplasm in the tube showed a clear region at the tip. The ultrastructure of C. amoenum pollen showed a bilayered exine, with the intine being very thick at the pores, and elsewhere having large intrusions into the plasma membrane. The cytoplasm was dense with vesicles packed with inner tube cell wall material. Golgi apparatus producing secretory vesicles, and mitochondria were found throughout the tube. The tube wall was bilayered; both layers being fibrous and loosely packed. • Conclusions: It is proposed that, for Conospermum, initial pollen tube wall constituents are manufactured and stored prior to pollen germination, and that tube extensi