Frank E. Round

The taxonomy of the Chlorophyta. II

The taxonomy of all the algal groups possessing both chlorophyll a and b is discussed for the levels above that of the family. Much of the discussion is related to previously conceived taxa but some new combinations are proposed. The subdivision of ‘green’ algae into Euglenophyta, Prasinophyta, Charophyta and Chlorophyta is discussed in the light of recent publications. The problem of further subdivision in the Chlorophyta is reviewed and the need stressed for more extensive electron microscopical and biochemical evidence. Until such data are available the author favours maintaining a large number of orders but also the rejection of those based on single characters.

Persistent, vertical-migration rhythms in benthic microflora

Abstract The diurnal migratory rhythm of the epipelic diatom association of freshwater streams has been investigated in laboratory studies. Movement of the diatom flora up to the surface of the sediment and down beneath the surface occurs once every 24 hours reaching a peak of cell numbers at the surface at approximately the same time each day. This migratory movement persists in the laboratory for at least eleven days under alternating light/dark conditions. It is also expressed in continuous darkness but the number of cells migrating is less than under conditions of alternate illumination and darkening. In continuous illumination the rhythm is disturbed. All the common diatom species behave in approximately the same way as the population. From the data, the existence of three separate rhythms of motility, phototaxis and geotaxis have been deduced. During the first half of the light cycle the cells increase their motility and become positively phototactic and during the latter half of this cycle they los...

Primary production and standing crops of epipsammic and epipelic algae

The ‘potential’ primary production of the epipelon and epipsammon of Shear Water has been estimated and related to standing crop parameters over a period of thirty months. Data have also been obtained for the ‘potential production’ of the flora in short cores from the same site. Standing crop and production of the epipsammon was always greater than that of the epipelon. The correlation between standing crop and production is closer for the epipelon than for the epipsammon owing to the retention of dead cells in the latter community.

The epipsammon; a relatively unknown freshwater algal association

Abstract A freshwater diatom flora has been shown to exist on sand grains. The species have been determined from samples of four bodies of water. This epipsammic flora is composed of minute diatoms, many of which require electron microscope study before their identification can be made certain. The chemistry of the water undoubtedly influences the association of species.

Observations on standing crops of epipelic and epipsammic algal communities in Shear Water, Wilts

Methods of estimating the standing crops of epipsammic diatoms have been evaluated and compared with those used for epipelic algal crops. Good correlations between chlorophyll a content and cell counts were obtained for epipelic populations, but because of the presence of large numbers of decaying cells, inseparable from living cells, such correlation was not obtained with epipsammic algae, even after correction of the pigment estimates for the presence of pheophytin a. The standing crop of epipsammic algae was at all times greater than that of epipelic algae at the same sampling station, and this was attributed to the differential effects of sediment disturbance by burrowing animals and water movements.

Patterns of seasonal succession of freshwater epipelic algae

The seasonal succession of algal species in the epipelon of two small pools over a period of three years is described in relation to changes in silica, nitrate-nitrogen and phosphate-phosphorus concentrations in the water above the sediments. Recurring patterns of seasonal growth of the various species are discussed.

Validation of the centric diatom genus name Cyclostephanos

The diatom genus Cyclostephanos Round is invalidly published because a legal type was not designated at the time of description. Round apparently intended for Stephanodiscus novaezeelandiae Cleve to be the type of the genus. That species is proposed here as the lectotype of the name Cyclostephanos and a lectotype is proposed for the name S. novaezeelandiae. Names of species placed in Cyclostephanos are here validated according to the rules of botanical nomenclature.

Studies on freshwater Amphora species. I: Amphora ovalis

Amphora species collected from British rivers and lakes have been studied by scanning electron microscopy. The original aim was to check on the distribution of the three widely reported species (A.ovalis, A.ovalis var. affinis and A.pediculus) in rivers and lakes and determine any variation in morphology. In the event numerous forms of each species were discovered and this paper deals with those of Amphora ovalis. The existence of morphological forms (phenodemes) in diatoms is discussed briefly. Amphora valves are asymmetric and the terminology of the various parts are discussed in relation to terms used by earlier workers. The type of A.ovalis and four other forms of A.ovalis have been photographed in the SEM and these are briefly described. The forms have been designated A-D and not given names.

Some observations on polarity and regeneration in Enteromorpha

The regeneration of two types of Enteromorpha has been investigated. Small tubular sections cut from the thallus develop rhizoids along the basal cut edge and papillae from the apical cut edge. The capacity for regeneration is greatest in segments from the middle and base of the thallus and least in apical sections. Regeneration in various liquid culture media at different light intensities and temperatures and on solid agar media has been tested. The addition of growth substances and extracts from Enteromorpha thalli always stimulate regeneration but in no way alter the polarity. The results are compared with previous conflicting accounts of regeneration of Enteromorpha.

THE ANTARCTIC DIATOM SYNEDRA REINBOLDII: TAXONOMY, ECOLOGY AND TRANSFERENCE TO A NEW GENUS, TRICHOTOXON

The bow-like Antarctic diatom Synedra reinboldii often occurs in great masses in the waters around the continent. One such occurrence provided material for a study of this taxon by electron microscopy. The nomenclature of this taxon is confused and we give details of its history. The structure of the valves is not at all like that of Synedra and a comparison with other elongate araphid genera leads us to the conclusion that S. reinboldii must be accorded separate generic status; we have selected the name Trichotoxon. Details of the distribution of Trichotoxon are discussed.