Stem segments with 3-5 leaf axils, excised from the upper portion of the mainstem of 2-year-old hoop pine (Araucaria cunninghamii Aiton ex D. Don) seedlings, produced orthotropic buds from the concealed axillary meristems when cultured on a basal medium (BM) of half-strength Murashige and Skoog (MS) inorganic salts, the medium level of growth factors and amino acids of de Fossard, 20 g L sucrose and 6.5 g/L agar. This procedure was also successful with A. balansae, A. bidwillii, A. colurnnaris, A. hunsteinri, A. luxurians, A. montana, A. rulei, A. scopulorum and Agathis robusta and with stem segments from orthotropic coppice shoots of juvenile morphology collected from the stumps of 20-year old hoop pines felled near ground level. The hoop pine explants were highly sensitive to cytokinin; 1 μM and 10 μM 6-benzylaminopurine caused the formation of distorted buds and total inhibition of bud development respectively. Lofier concentrations (0.001-0.1 μM ) did not noticeably influence bud formation or development. A low rate of multiplication was induced by reculturing the stem segments after the excision of the initial shoots. New buds developed in the leaf axils of that part of the initial shoot which remained attached to the primary stem explant. Shoots derived from seedling and coppice cultures of hoop pine and seedling cultures of Agathis robusta rooted in vitro on BM + 0.1-10.0 μM indole-3-butyric acid (IBA), but with only 5-20% success. Up to 80% rooting was obtained if both hoop pine shoot types (i. e. from seedling and coppice cultures) were cultured on modified BM (quarter strength MS salts, 10 μM IBA plus no agar) for 2 weeks, before being transferred to a mixture of non-sterile peat and perlite or vermiculite and perlite, maintained under a high humidity (90-95%). Plantlets were subsequently transferred to normal glasshouse conditions and then to the field with less than 5% mortality. Thus hoop pine can be added to the relatively small number of conifers for which the capacity to micropropagate juvenile and mature plants and successfully establish their clones in the field has been demonstrated.

Embryo development following suspensor elongation was studied in three species of Araucaria: A. cunninghamii, A. heterophylla and A. bidwillii. The mature embryos of these species were compared with those of A. hunsteinii and species for which published data are available. In general outline, the embryogeny of Araucaria resembles that described for a number of other conifers. Differences are evident among species of Araucaria with respect to the following features of the mature embryo: overall size; relative lengths of the cotyledons, hypocotyl and root cap; cotyledon number; the presence of stomates; the extent and arrangement of the vascular and secretory tissues; and the state of differentiation of the vascular tissue. Consideration of all these features lends some support to the generally recognized division of the genus into four sections, although there is some evidence to suggest a relationship between the Eutacta and Intermedia species, on one hand, and the Columbea and Bunya species, on the other.

Pollination was studied in three species of Araucaria: A. cunninghamii, A. heterophylla and A. bidwillii. More limited observations were made for A. hunsteinii and A. angustifolia. The investigation revealed considerable variation among species of Araucaria with respect to pollination features. The bract scale of the receptive cone of both A. cunninghamii and A. heterophylla has a stoma-free furrow which directs pollen grains onto a thin flange on the tip of the ovuliferous scale. The bract scale of A. bidwillii bears stomata over most of its surface, and is broadly scalloped so that pollen grains are deposited in a band across both bract and ovuliferous scales. On germination, the pollen tubes of these three species penetrate the epidermis of the scale and for a short distance grow beneath the surface before emerging and travelling, without branching or major deviation, towards the proximal end of the ovuliferous scale. On reaching the micropyle, the pollen tubes enter the nucellus. In known features, pollination in A. hunsteinii resembles that in A. bidwillii. The pollen tubes of A. Angustifolia bear short branches and, in distal regions of the scale, are erratic in their orientation. Results are discussed in relation to pollination mechanisms in other conifers and to taxonomic divisions within the Araucariaceae.

The development of the seed coat, seed wing and food reserve tissue of the female gametophyte was studied in four species of Araucaria: A. cunninghamii, A, heterophylla, A. bidwillii and A. hunsteinii. The means of seed dispersal in each of these species were also recorded. Comparisons were made among these species and others for which published data are available. The species differed with respect to the thickness of the seed coat and anatomical characteristics of the component layers; the thickness and nature of the nucellar layer; the relative degree of enlargement of non-fertilized ovules; the composition of the food reserves; the presence and nature of the seed wing; and the seed dispersal mechanism. The distribution of these features among the species of Araucaria for which data are available is consistent with the generally followed division of the genus into four sections.

Development of the proembryo and suspensor was studied in three species of Araucaria– A cunninghamii, A. bidwillii and A. heterophylla. In all species there are six synchronous free nuclear mitoses followed by wall formation. The subsequent internal division gives rise to a typical U.S.E. conifer proembryo. although the E group includes the conspicuous symmetrical cap, and the U cells are very ephemeral. During all divisions the proembryo is situated in the central region of the archegonium. The cells of the S group subsequently elongate to form the functional suspensor. Cleavage polyembryony does not occur although simple polyembryony is common. The proembryo of Araucaria is considered to have diverged at an early stage of evolution of the conifer proembryo, but to have subsequently undergone considerable specialization in a direction unrelated to evolutionary trends recognizable among other conifers.