Genotypic succession in the cyclomorphosis of Bosmina longirostris (Cladocera)

SUMMARY. The pattern of cyclomorphosis of Bosmina longirostris was followed over a 21-month period in Lake Travis, Texas. Appreciable variation was observed in body size and in the lengths of antennules and mucrones. Electrophoresis of clonal isolates collected over the period of study showed a seasonal cycle in esterase phenotypes. A definite association was demonstrated between the esterase phenotypes and morphologies of these clonal isolates. Individuals of one esterase phenotype were usually large and long-featured, whereas individuals of the other esterase phenotypes were smaller, with short features. The association of morphology and esterase phenotypes from laboratory experiments corresponded to the association observed in field samples. These results support the hypothesis that the cyclomorphosis of Lake Travis Bosmina involves a succession of clones as well as phenotypic plasticity.     

Methods for the isolation, sterilization and cultivation of Lemnaceae

SUMMARY. A method is described for isolating and sterilizing fronds of Lemnà gibba, L. minor, L. trisulca, L. polyrrhiza and Wolffia arrhiza , employing enrichment followed by sodium hypochlorite treatment. The method enables about 4% of the total number of treated fronds to be used as initiators of clonal cultures in which bacteria responding to organic enrichment and algae are excluded. Appropriate growth media, culture vessels and culture conditions are detailed.     

Succession following wildfire in coastal heathland (Nadgee Nature Reserve N.S.W.)

Changes in coastal heath vegetation were measured for 6 years following a wildfire and the data compared with the pre-fire vegetation. For the first 2 years changes were related to time; after that environmental factors dominated the process of regeneration. During the first 4 years plant species spread rapidly and maximum species diversity per plot was reached 4 years after the fire. About the same time many species consolidated their position in the community; this being shown by cover levels greater than before the fire for some species. Six years after the fire the vegetation is still dynamic and very different when compared with the heath before burning.     

Genotypic Responses to Auxins in Tissue Cultures of Phaseolus

Responses of seven Phaseolus genotypes to the four auxins picloram, 2,4-D, NAA and 1AA, in tissue cultures, were examined. Callus growth was promoted by picloram and the range of effective concentrations for most genotypes was broad. The auxin 2,4-D also enhanced callus growth, but the range of optimal concentrations was markedly narrower than that of picloram. NAA when supplied at relatively high concentrations gave good growth. IAA was ineffective in supporting callus growth. The differences in 2,4-D concentrations required for optimal growth and the differential responses to low concentrations (0.04–1.25 μM) of picloram between several genotypes tested were large. These genotypic variations in auxin responses were repeatable and may thus reflect genetic differences.     

The pteridophytes of Mauritius (Indian Ocean): ecology and distribution

A survey of the pteridophytes of Mauritius is presented, including a summary of their habitats, ecology, and phytogeographical affinities. Of the 186 infrageneric taxa recorded from the island, 8 are adventive or naturalized, and 27 are presumed rare or extinct. Major ecological groupings are presented and species are listed for both indigenous and secondary plant communities.     

On the Organization of the Naked Filose Amoeba,Nuclearia moebiusi Frenzel, 1897 (Sarcodina,Filosea) and Its Implications1

The ultrastructural organization of Nuclearia moebiusi is described. The organism has filose pseudopodia without supportive microtubules; it has mitochondria with flattened cristae, lacks extrusomes, microtubule-organizing centers, and cytoplasmic microtubules. During cell division, microtubules appear only within the nucleus, and reorganization of the nuclear envelope occurs late in the nuclear division cycle. Ultrastructural studies reveal that Nuclearia spp. have a pattern of cellular organization distinct from that of other amoebae. Comparison of ultrastructural features suggests that this organism is only distantly related to other rhizopod amoebae (including other filose amoebae) and to the heliozoa.     

Characterization of Plant Epidermal Lens Effects by a Surface Replica Technique

Optical replicas of leaf surfaces were made for characterizingthe lens properties of individual epidermal cells. Using a dentallatex, moulds were made of leaf surfaces and subsequently usedto produce agarose replicas. The replicas focused light in amanner similar to intact epidermal cells and it was possibleto measure both focal lengths and intensifications within leafreplicas of Thermopsis montana, Mahonia repens, and Smilacinastellata which had epidermal cells of different diameter. Focallengths ranged from 74—130 µm which indicated thatlight was concentrated within the underlying photosynthetictissues of these leaves. Focal intensifications were measuredsensiometrically and were 1.5 for T. montana and 2-6 for theother species. These values compare favourably with calculatedfocal lengths and measurements taken from isolated epidermallayers. The results indicate that the epidermis can concentratelight within the leaf to amounts well in excess of ambient light.Furthermore, the replicas faithfully reproduced fine anatomicaldetails from a wide variety of leaves and they provide a non-destructiveway to reproduce surface characteristics for anatomical andphysiological studies.