indiscriminately by the same bee or fly. At this time, the same vectors were observed visiting P. prostrata plants. Few insects were seen on any one P. traversii plant. While it was noticed that flies and Halictus worked systematically over a flower head in the othe species, in P. traversii, Crysophanus sallustius was seen to be present for long periods and is an important vector.

Most P. traversii individuals flower later than the other Cass species, and most of the individuals grow amongst thick scrub, so that this may account for different animal populations on P. traversii. However, a number of single plants of P. traversii are mixed with all the other species in some areas and flowering times overlap. Similarly P. prostrata, P. “snow tussock” and P. “short tussock” are all juxtaposed in some places and these all have overlapping flowering times. In any one day the P. “snow tussock” plants, growing in shady places, are visited for shorter times by the sun-loving flies, butterflies and bees than are P. prostrata and P. “short tussock” in open sunlight. Some P. “snow tussock” plants grow on fans and exposed places, however.

No night flying insects have been taken into account in describing pollinating agents, but many moths are found in the tussock country. The scented white flowers of P. prostrata, P. “short tussock” and P. “snow tussock” no doubt attract night flying insects. Since distances between different Pimelea species, flowering at the same time, are not great in some places at Cass (some are only feet apart), the physical possibility of cross pollination between species as well as outbreeding within species is important in considering hybridization and variation. The non-selectiveness of unspecialized vectors may help to account not only for similarity in flowers in different Pimelea species but for the amount of hybridization taking place. (See Thomson, 1880, 1927). A. number of the same insects have, in fact, been captured on as widely different genera as Aciphylla, Leptospermum, Leucopogon, Brachycome, Celmisia and Hypochaeris, but when Pimeleas were in full flower other profuse flowerers like Leptospermum were not yet out. It was not ascertained whether one individual Halictus restricted itself to one genus or not.

The effect of heavy rainfall on pollination and fruit set is difficult to gauge. In the 1957-58 summer it appeared to have had considerable significance in decrease of total fruit set. The flowers of one head may be opening over a period of a little more than a week, and the flowers of each plant over a two-week period. They soon wither and die when fruit begins to form or if they are unpollinated. Most plants of any one taxon in a given area flower together. If some catastrophe occurs this may result in a reduction in numbers of fruit set. As a general observation, it was noticed that much more fruit were set, especially in P. “short tussock” and hybrids in the summer of 1956–57. P. traversii and P. prostrata were less affected. Heavy continuous rain affects not only the ability of insects to fly and seek nectar, but it may drown out such ground dwellers as Halictus and also fills floral tubes with water, washing pollen off anthers. The most favourable weather for animal activity and for optimum attractiveness to animals of Pimelea flowers is the hot, dry, sunny weather usually experienced at flowering time.