Gynodioecy in Pimelea

In the most careful description of polymorphism in Pimelea flowers yet published, Thomson (1880) concluded that P. prostrata, “Though hermaphrodite in structure… is dioecious in function and will probaly tend rapidly to become so in structure as well”. Thomson described hermaphrodite forms where the style lengthened after the flowers opened until it extended beyond the anthers. Other dioecious forms had large male flowers on some individuals and smaller females on others. In the former, the short style, with tiny stigma, lengthened and protruded between the lobes of the flower tube, although the ovary then shrivelled. The female plants had flowers with a long style, a large capitate stigma and aborted anthers. P. longifolia was described by the same writer (Thomson, 1927) as being polygamous and dioecious.

Cheeseman (1925) gives as a generic character for Pimelea that the flowers are hermaphrodite but functionally dioecious or occasionally polygamo-dioecious and that “The male flowers are the most numerous….” Cheeseman designates as polygamo-dioecious³, erroneously, some 10 of the species described by him in the “Manual” including P. traversii and P. prostrata. The other species he describes are not classified, as to breeding system. Cheeseman (1914), figured four species and gave similar details. Parlane (1925) wrote about floral features in Pimelea but followed Cheeseman.

Dr. E. Godley (pers. comm.) has found that P. longifolia and P. virgata are gynodioecious. He has noted that in the specimens used by Cheeseman for the illustrations of P. longifolia (sheets 5336.1 and 5336.2 in the Cheesemand herbarium) all hermaphrodites have protruding styles so that the male flowers described by Cheeseman are not present. It seems probale that Cheeseman had observed hermaphrodite flowers in different stages of development.

As well as for the four species at Cass, the present writer has observed that P. aridula, P. sericeo-villosa, P. pseudo-lyalii and P. arenaria have female and hermaphrodite flowers on separate plants. It will be shown that on functional grounds also the Cass Pimeleas are gynodioecious.

Australian and Tasmanian writers, Black (1952) and Cruickshank (1953) have not used the term gynodioecy for the type of breeding system in Australian Pimelea spp. The former says of the genus, that species are “bisexual or unisexual by abortion of stamens or ovary, often diocious”. The latter describes some species as dioecious. It appears that there is greater variation in types of breeding system in Australia than in New Zealand. Descriptions of some of the large number of Australian species of Pimelea (Bentham, 1873) leave little doubt, however, that gyno-