Research on flower biology began in New Zealand in the early 18705 under the influence of Darwin' s work on orchids. but from the tum of the century there was a decline in interest until the 1950s. Spring and summer are the main flowering periods. but many species flower in winter and examples are described. Of some 1800 indigenous species of flowering plants 12-13% are dioecious. c. 2% gynodioecious. and 9% monoeciou5. But in many cases the unisexuality is characteristic of a widespread family or genus and cannot be claimed as having evolved in New Zealand. The morphological differentiation between male and female flowers settles down at a level characteristic of the genus and the degree of differentiation need not reflect the time since differentiation began. In hermaphrodite species heterostyly is not known. and demonstrated examples of self-sterility are few. A classification of 649 species with attractive flowers gives 60.6% white. 17.2% yellow. 12.4% blue lilac or dark purple. 5.7% red to crimson. and 4% green. A large sample from the British Isles has 25.1% white flowers. It is emphasised the flowers classified as white are rarely completely so. that a white plus yellow group is important. and that not all the flower colours need have evolved under New Zealand conditions. Nectar and honey-dew from native plants provide useful honey sources. but work on nectar has been confined to cases of bee poisoning. Available pollinators are birds (7 spp.), bats (I sp.). butterflies (16 spp.), and solitary bees (c. 40 spp.) as well as many species of moths. beetles. and flies and several introduced bees. The general impression is of widespread self-fertility in hermaphrodite plants and variety in respect of insect visitors. It is emphasised that although much attention, everywhere, has been given to methods of pollination, more attention should be given to the results. i.e., the percentage of ovules which produce seeds. And it is also emphasised that a better understanding of the characteristics of New Zealand flowers wiIl be obtained by studying their relatives in other lands.
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INTRODUCTIONFloras of New Zealand, including the current volumes (Allan 1961. Moore & Edgar 1970 have always included useful information on flowers, their gender, colour. and flowering times. But the first paper on flower biology appeared soon after the subject entered its modem phase in the Northern Hemisphere. In IS73 Cheeseman described the pollination mechanism of an orchid. Pterostylis trulli/olia. This began 30 years of observations on native plants. a period reviewed in two important papers by Thomson (IS81a, 1927). Then. from the tum of the century, interest in flower biology waned, and except for the work of Heine (1938) other branches of ecology were favoured. But from the I 950s onwards interest revived, and some aspects of recent work were reviewed by Hair (1966).