Buckman's Paradox: variability and constraints on ammonoid ornament and shell shape

Buckman's Law of Covariation states that ammonoid shell shape and ornamentation are typically correlated, such that compressed, involute forms have light ornament while more inflated, evolute forms have heavier ornament. Such covariation has been observed in many ammonoid groups, and implies a link between the morphogenesis of shell shape and ornamentation. However, other evidence suggests that while ornament growth is controlled by the genetic‐developmental program of the ammonoid, shell shape is strongly influenced by environmental factors. These differing viewpoints lead to Buckman's Paradox – are ornamentation and shell shape tightly linked, as implied by Buckman's covariation, or is the morphogenesis of ornament controlled genetically, while shell shape is controlled environmentally? To address this issue, the variability of shell shape and rib morphology has been compared for a group of endemic acanthoceratid ammonites from the Cretaceous Western Interior Seaway of North America. If Buckman's Law holds due to a morphogenetic connection between shell shape and ornamentation, we would expect taxa with more variable shell shapes to also show more variable rib features and growth. Morphometric analysis of seven shell shape and two rib characters for the Western Interior acanthoceratids finds no such correlation, suggesting that shell shape and rib growth are controlled by different processes. Indeed, rib growth appears to be more constrained than shell shape, consistent with the view that ornamentation is more tightly controlled by the developmental‐genetic growth program of the ammonoid. These results emphasize the complexity of ammonoid morphogenesis and highlight our limited understanding of the causes underlying Buckman's Law.     

A world-wide survey of the microflora of Dactylis glomerata seed*

The fungal microflora of orchard (cock's-foot) grass seed (Dactylis glomerata L.) was determined for 140 samples obtained from thirteen countries. The microflora was assessed by visual examination of dry seed (20–50 x), by microscopic examination of centrifuged seed washings and by incubating seed on 2 % malt extract agar (MA) under a 10-day regime of diurnal cycling of temperature (23-9^oC/i8-3^oC) and near-ultraviolet radiation (12 h NUV/ 12 h dark). More than twenty-five species of potentially pathogenic fungi and forty species of saprophytes were detected. The pathogens included an Ascochyta sp., Botrytis cinerea, nine species of Drechslera including D. dactylitis (infested 23% of seed lots) and D. Useptatum (10% of seed lots), five species oiFusarium including F. avenaceum (5 % of seed lots), Lep-tosphaeria sp., Phleospora sp., Phoma sp., Phomopsis sp., Pyrenochaeta sp., Rhizoctonia sp., Rhynchophoma sp., Septoria sp. and Stagonospora sp. Many more fungi were identified from seed plated on MA and exposed to NUV than by examination of seed washings or visual examination of dry seed. Several of the fungi that were detected are known to produce mycotoxins.     

Microbiological Synthesis of Fat: THE EFFECTS OF VARYING PH, TEMPERATURE, NITROGEN, INCUBATION PERIOD, AND SUGAR CONCENTRATION ON FAT-PRODUCING MOULDS

1. A more detailed study has been made of the influence of thesefactors on fat formation by Aspergillus nidulans, Penicilliumspinulosum, and Penicillium javanicum. 2. The effect of halving the glucose, while keeping the ammoniumnitrate concentration constant, lowered the yield of fat onsugar used in A. nidulans and P. spinulosum but not in P. javanicumcultures. 3. Keeping the same N: C ratio and raising the glucose concentrationfrom ro to 20 per cent. showed that to per cent. glucose wasmore efficiently converted to fat by A. nidulans and P. javanicum. 4. The iodine values of the extracted fats were higher, in general,with increased length of incubation. Low ammonium nitrate concentrations,however, tended to give low iodine values. 5. The results have been applied on a larger scale by growthin Roux bottles, Glaxo flasks, and a flat stainless-steel tank.     

A new hexaploid Be He v alia (Hyacinthaceae) from European Turkey

ÖZHATAY, N, JOHNSON, M. A. T., MATHEW, B. & DALGIQ, G., 1991. A new hexaploid Bellevalia (Hyacinthaceae) from European Turkey. A new species of Bellevalia Lapeyr. from the vilayet of Edirne in European Turkey is described which is hexaploid; 2 n = 24. This is a new chromosome number for Turkish material of the genus. Relatives and possible origins are discussed.     

The Effect of Gibberellic Acid on Fibre-cell Length

Measurements were made of fibre-cells from plants of Corchorusolitorius L., Hibiscus cannabinus L., and Cannabis sativa L.Which had been sprayed with gibberellic-acid solution. Fibre-cellsfrom treated plants showed a highly significant increase inlength, 20–130 per cent, for the whole stem and as muchas 400 per cent. for a single intermode. Gibberellic acid increased the variation in cell-length andthe positive skewness of the distribution of the variate. Differences in cell-length can be related to the developmentalsequence of the shoot and the variation in internode-length.