Pollen and the origin of the Australasian Anemones (Ranuncu-laceae)

In the whole of Anemone section Rivularidium , to which the two Australasian species ( A. crassifolia and A. tenuicaulis ) belong, pollen like that of A. tenuicaulis (Cheeseman) Parkin & Sledge has been found elsewhere only in the three South American species, A. antucensis, A. helleborifolia and A. peruviana. Itseems evident, therefore, that A. tenuicaulis originated in South America. Within Anemone , the pollen of the other Australasian species, A. crassifolia Hook., resembles only that of the A. hortensis group, which is placed in another section and occurs in the Mediterranean region. The taxonomic position of A. tenuicaulis is also discussed, and it is concluded that this species occupies an isolated position in sect. Rivularidium.     

Contribution to the flower structure of Sararanga (Pandanaceae)

In Sararanga , the fruit is a berry as in Freycinetia. The testa comprises a lignifled outer integument with several cell layers, and an unlignified inner integument with two cell layers. Abortive fruits are frequent; they correspond to normal fruits that do not have carpels and sometimes have a lateral process that suggests an abortive carpel. The staminate flowers have a pistillode as in Freycinetia. The anther walls have 1–3 cell layers with endothecial thickenings, one layer in the distal part, 2–3 layers in the proximal part, as in Pandanus. Thus, within the family Pandanaceae, Sararanga has an intermediate position between Pandanus and Freycinetia. Generally speaking, there is a gradient in the vascularization of the bracts on the inflorescences: upper bracts are unvascularized, lower bracts vascularized. Anatomy suggests that the cupules are a perianth.     

Carpellodes or staminodes? Problems in the genus Pandanus (Pandanaceae), and their taxonomic significance

Carpellodes or staminodes? Problems in the genus Pandanus (Pandanaceae), and their taxonomic significance. The staminodes of the male flower of Pandanus palustris (section Megakeura) and the carpellodes of that of P. barklyi (section Barklya) were studied by both light microscopy and SEM. Comparison of these staminodes and carpellodes with those of the male flowers of P. androcephalanthos, P. hermaphroditus, and P. kariangensis (section Martellidendron), and with the staminodes of the male flower of P. brosimos (section Karuka) revealed that the staminodes are devoid of fibres, each having a single vascular bundle, whereas the carpellodes contain several strands of fibres, each associated with a vascular bundle. These distinctive characters are identical to those differentiating the stamens from the carpels in the genus. These staminodes and carpellodes are of taxonomic value, since they vary markedly between the species, though their main structure is similar within each section. In P. barklyi the male flower had no genuine column, and the filaments were fused to form a staminal tube.     

On a new subsection of Pandanus section Cauliflora (Pandanaceae) with paniculate staminate inflorescence structure,distinctive leaf anatomy and pollen morphology

A new subsection, Pandanus section Cauliflora subsection Paniculiflora, is described to contain P. halleorum, on the grounds of the paniculate structure of its staminate inflorescence, a feature not known elsewhere within the genus Pandanus. Both leaf anatomy and pollen morphology appear to support this taxonomic separation.     

Flower structure and potential bisexuality in Freycinetia reineckei (Pandanaceae), a species of the Samoa Islands

In Freycinetia reineckei the staminate flower (on the staminate spikes) comprises 3 or 4 (sometimes 2) stamens and a pistillode with 2 (sometimes 4) carpellodes, and the pistillate flower (on the pistillate spikes) is formed of a pistil with 2 (sometimes 4) carpels and of 3 or 4 (sometimes 2) staminodes. This perfect floral homology, also observed in all the other species that were studied with both pistillate and staminate material, strongly suggests that the flower of Freycinetia is basically and potentially bisexual, and may explain the occasional sexual lability and bisexuality of that flower (occurrence of both pistillate and staminate inflorescences, and/or of bisexual inflorescences with bisexual flowers and/or unisexual flowers, on the same individuals) in some species, and also the frequent occurrence of bisexual spikes in this species. These may be partitioned into pistillate, staminate, mixed and sterile zones. In the pistillate zones the flowers have the same aspect and structure as the pistillate flowers. In the staminate zones the flowers generally comprise 3 or 4 (sometimes 2) stamens and a ‘semi-pistil’ some have both stamens and staminodes. The semi-pistils are intermediate between pistils and pistillodes in length, aspect and structure, but always have placentas and ovules. In the mixed zones the flowers are generally formed of a pistil and 3 or 4 (sometimes 2) stamens, and are therefore true hermaphrodite flowers; some have both stamens and staminodes. In the sterile zones the flowers comprise a semi-pistil and 3 or 4 (sometimes 2) staminodes. The staminodes are anatomically very similar to the stamens, especially in the staminate, mixed, and sterile zones, in which they exhibit a wide range of variation in length, aspect and structure. The perfect floral homology as generic character on one hand, and the occasional bisexuality both with and without bisexual flowers and other aspects of sex expression (e.g. occurrence of both pistillate and staminate shoots on the same individuals) in some species on the other hand, seem to indicate that Freycinetia is a basically monoecious, sex changing genus.