Development of the filiform pollen of the sea nymph Arnphibolis antarctica (Labill.) Sonder & Aschers. ex Aschers. has been characterized by high resolution light and electron microscopic methods. First pollen mitosis occurs at the end of the young spore period immediately preceding the vacuolate period, in contrast to many terrestrial pollens. Mature pollen is trinucleate, and is spirally coiled within the anther. The mature pollen wall shows a positive reaction for acid phosphatase like the intine of terrestrial pollens but is devoid of the outer exine layer, as judged by light and electron microscopic evidence. Development and arrangement of Thalassodendron ciliatum (Forssk.) Den Hartog pollen are similar. The adaptation of the pollen of aquatic plants for submarine pollination is reviewed in the light of evidence from 18th and 19th century work.

The two species of sea nymph, Amphibolis antarctica (Labill.) Sonder & Aschers, ex Aschers. and A. grifithii (J. M. Black) Den Hartog, are endemic to Australia. They have distinctive leaf morphology, and stem and rhizome anatomy. Environmental and ecological factors that limit the distribution of both species in southern Australia are considered. Both species support a wide range of algal and other epiphytes, and a list of the common epiphytic biota is presented. Penetration of the host tissue by epiphytes is seldom observed.

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The distribution of microfungi in an Australian heathland soil has been investigated. Unlike the typical distribution for soil organisms, the numbers did not decrease progressively with depth, for the B horizon showed a comparable population both in numbers and types to that of the A1 layer even at depths of 60 in. or more. This distribution is correlated with the organic carbon content of the ortstein layer. The results obtained from the direct and indirect methods for determining the numbers of fungi per gram of soil were compared; from this comparison evidence was gained to support the statement that the suspension technique gives a fair picture of the soil population and does not reflect a high sporing capacity of a few fungi, as has been so often stated. One hundred and seven species of fungi have been isolated from this soil. Mortierella ramanniana is the commonest fungus and it occurs right through the profile. The genus Penicillium with its multiplicity of species is the dominant genus. Several species of Aspergillus appeared frequently on the plates and it is this genus which provides the forms that characterize this particular soil, including three new species of the genus. All the other fungi that were isolated have been recorded from northern hemisphere soils and are part of a cosmopolitan soil flora. Ascosporic and sclerotial types characterize the litter fungi and those forms associated with plant parts in the soil, rather than the general fungal soil flora.