A new species of the conifer Frenelopsis from the Cretaceous of Sudan

Conifer fragments from the Lower Cretaceous of Sudan are preserved as internal and external silica moulds. Low viscosity silicone rubber has been used to prepare casts showing fine epidermal details which enable identification of the plants. One is I'seudofrenelopsis parceramosa (Fontaine) Watson, the other is described as a new species of Frenelopsis Schenk.     

Patterns of arrangement of lateral appendages on axes of Stigmaria ficoides (Sternberg) Brongniart

The arrangement of lateral insertions has been examined on axes of Stigmaria ficoides . The arrangement can be considered as a phyllotactic pattern made up of parastichies and orthostichies. Orthodox phyllotactic patterns, based on parastichy numbers from the Fibonacci or common accessory series, do not occur. Instead spiral (or multijugate) arrangements occur based on pairs of parastichy numbers such as x and x + 1, x and x + 2, x and x + 3, etc. and x ranges from 12 to 19. Whorled arrangements occur relatively infrequently. Individual axes commonly show frequent changes in pattern. The observations are used to make deductions about the growth and homology of stigmarian axes.     

Growth characteristics in co‐occurring Upper Ordovician species of the tabulate Catenipora from southern Manitoba,Canada

Four species of the tabulate coral Catenipora are present in the Selkirk Member of the Red River Formation at Garson, Manitoba. They provide an opportunity to compare the growth characteristics of multiple, co‐occurring species that produced cateniform coralla. Corallite increase, cyclomorphism and other growth features show high variability within and/or among the species. A total of five types of lateral increase and two types of axial increase are recognized. Lateral increase accounts for over 80% of all occurrences of corallite increase in each species, with the four species differing significantly in the relative frequency of the various types of lateral increase. The type of axial increase, megacorallites and agglutinated patches of corallites that developed from normal, undamaged corallites in C. foerstei are species specific. In all species, cyclic fluctuations in the tabularial area of corallites are considered to be annual, and the variable growth rates within colonies and species are attributed to differences in astogenetic stages or environmental conditions. Average annual vertical growth was positively correlated with average tabularial area in C. foerstei, C. cf. robusta and C. rubra. Catenipora cf. agglomeratiformis, however, which had the lowest average tabularial area and greatest sensitivity to sediment influx, had a high average growth rate comparable to that of C. rubra, which had the largest average tabularial area. The formation of ranks or lacunae by certain types of lateral increase seems to have been the most effective strategy for maintaining and/or expanding the colony growth surface in all four species, and was most common in C. cf. agglomeratiformis. A reptant growth pattern, characterized by creeping ranks, permitted effective recovery of damaged parts as well as quick formation of new ranks or lacunae. The growth surface of these species was situated near the sediment–water interface. □Growth characteristics, intraspecific variation, interspecific variation, palaeobiology, tabulate corals.     

The Effect of Antibiotics on the Ultrastructure and Photochemical Activity of a Developing Chloroplast

The effects of the antibiotics chloramphenicol and cycloheximideon the ultrastructure of the chloroplast in greening cells ofEuglena gracilis strain Z have been investigated. The rate ofchloroplaat development in the presence of either antibioticwas closely related to that of chlorophyll production. Chloramphenicol,which at 10 mg/ml inhibits chlorophyll synthesis but not celldivision, caused a marked inhibition of the development of chloroplaststructure. The chloroplasts were smaller than those of untreatedcells and contained a smaller number of internal lamellae. Mostof these lamellae were not appressed and the results supportthe suggestion that chloramphenicol inhibits the synthesis ofa protein responsible for the fusion of individual lamellaein the chloroplast. Measurement of the photochemical activityof chloroplasts isolated from chloramphenicol-treated cellsshowed that the photoreduction of NADP from water (photosystemI+II), photosystem II activity, and photosystem I activity weregreatly inhibited when compared with chloroplasts from untreatedcells. In contrast, cycloheximide at 2.5 to 5.0 µg/mlinhibited cell division but allowed the chloroplasts to developafter a lag phase, the length of which was related to the concentrationof antibiotic employed. The number of lamellae per chloroplastand the degree of appression of the lamellae in chloroplastsof cycloheximide-treated cells and untreated cells were comparable.After 48-h illumination the photochemical activities of chloroplastsisolated from cycloheximide-treated cells were about 50 percent of those of the untreated cells.