An architectural analysis of Archaeopteris9 a fossil tree with pseudomonopodial and opportunistic adventitious growth

Currently recognized hierarchies of lateral organs in Archaeopteris are presented and phenomena that mediate organography and organotaxis in the taxon are discussed. It is demonstrated that Archaeopteris is totally lacking extant architectural analogues, and the methodology employed in the architectural analysis of such fossil plants is introduced. Proposed growth categories or phases for the Archaeopteris plant are presented and tested against evidence from a large silicified log of Callixylon, the trunk of Archaeopteris. An architectural model is put forward that encompasses such growth phaseS. Finally, the occurrence of reiterative, opportunistic growth in Archaeopteris is discussed.     

Ultrastructural Study of Plasmodium knowlesi Antigen Used in Vaccination of Rhesus Monkeys*

SYNOPSIS. Material from various steps obtained in the French pressure cell technic of preparing antigen from Plasmodium knowlesi-infected red cells, was examined by electron microscopy. A positively charged colloidal iron solution was used to differentiate between membranes of host red cells and parasites. Red cell membranes take the stain, whereas parasite membranes do not. This antigen which has been used previously to protect monkeys against P. knowlesi appears to consist almost entirely of membrane-bounded vesicles. Some of these vesicles contain a fine granular material, whereas others appear empty. The antigen failed to stain with the positively charged iron solution, which suggests that it is free of contamination by host cell membrane.     

Methods for the Large-Scale Cultivation of an Oxytricha (Ciliophora: Hypotrichida)1

ABSTRACT. Oxytricha strains used in biochemical studies have traditionally been grown in unaerated, unagitated culture tubes or Fernbach flasks. These cultures are limited in volume to about one liter and have a very nonuniform distribution of cells, with the majority of the cells at the very top or bottom of the medium. We have found conditions in which Oxytricha can be grown in 50-liter fermentation vats. The cultures grow to a uniform density of about 6000 cells/ml.     

Differential staining for live and dead sperm of honey bees

ABSTRACT Seven staining techniques were modified and tested for differentially staining the live and the dead sperm cells for the honey bee (Apis mellifera L.). The eosin Y staining method was found to be a simple technique by which the live cells stain bluish purple whereas the dead cells stain bright yellow to greenish yellow. Therefore, it produces a strong contrast between the dead and live sperm cells, and appears to be the most suitable supravital staining method for evaluating the viability of honey bee sperm cells. The significance of supravital staining techniques in assessing the quality of sperm cells during cryopreserving sperm cells is discussed.     

Comparison of analysis of stomach contents and faecal samples from zebra

Stomach contents and faecal samples from the same individuals were collected and analysed from eighteen plains zebra in Kajiado district, Kenya. They were analysed microscopically using the point frame method (Chamrad & Box, 1964). The composition of the diets is expressed in terms of ‘parts’ (leaves, sheaths, and stems), while ten grass species which featured prominently in the diet are discussed. The results were tested statistically and regressions were drawn for leaf, sheath and stem proportions in stomach contents and faecal samples. The frequency of leaves appearing in the stomach was found to be consistently higher than that of the faeces while the reverse was the case for sheaths and stems. Out of about sixty species of grasses and five of sedges, the ten most important ones in stomach samples were also the most important species in faecal samples, although some appeared in different orders. All species which had a frequency of at least 3% in the stomach contents were identifiable in the faecal samples.     

Platypterygius australis, an Australian Cretaceous ichthyosaur

Sufficient material has been assembled to restore the powerful pectoral girdle and large fore limbs of Platypterygius australis (M'Coy). A reasonable approximation to the line of action of dorsal and ventral muscles which principally affected the trim of the low-set fin-blades was along the middle of the fin. Increased tension brought the fin-blades nearer horizontal (to a diving position) and varying amounts of relaxation during forward movement allowed mainly water resistance to increase the tilt. The flexible blade edges were crucial in this. Unequal tension on the blades would have caused turning of the animal with whatever rapidity was desired. Allowing both fin-blades to rise together to stalling point could have checked the animal abruptly as it struck prey. Large relative and absolute increases in the portions of the coracoids adjacent to the median symphysis highlight the relative development of young individuals. Positive allometric growth in this area stopped quite suddenly as the animals approached 6 m total length, leaving only general size increase.     

Studies on the Growth in Culture of Plant Cells: XI. THE INFLUENCE OF SHAKING RATE ON THE GROWTH OF SUSPENSION CULTUEES

The influence of shaking rates (expressed as revolutions permin) on orbital shaking platforms (1 in (2.54 cm) diam. rotarymotion) on the growth of cell suspension cultures of Acer pseudoplatanusL. and Atropa belladonna cultivar lutea Döll are described.By following cell growth and respiration and the levels of oxygenand carbon dioxide in the media during the progress of incubationit is concluded that the reduction of growth at sub-optimalshaking rates is not due to oxygen deficiency or toxic accumulationof carbon dioxide. The growth of the Atropa cell suspensionin ‘closed systems’ has been studied by the developmentof modified culture vessels and evidence obtained that the reducedgrowth in the systems is due to the formation by the culturesof an unidentified volatile growth inhibitor and not to eitheroxygen depletion or toxic accumulation of either carbon dioxideor ethylene. It is suggested that the reduced growth in ‘opensystems’ cultures at sub-optimal shaking speeds is eitherdue to retention of this volatile inhibitor or to restrictionof nutrient uptake by the existence of a stationary liquid-phaseboundary to the cells.     

Effects of density on the reproductive success of pine engravers: is aggregation in dead trees beneficial?

1. The pine engraver bark beetle Ips pini (Say) (Coleoptera: Scolytidae), aggregates primarily on dead or dying pine trees. In this study pine engravers were laboratory-reared on logs at a range of low densities to determine whether there was a fecundity advantage of breeding aggregations.
2. Mean reproductive success for both males and females declined exponentially with increasing density.
3. Female pine engravers had shorter egg galleries at higher densities, suggesting that they left high-density breeding sites earlier. This would reduce the number of eggs that failed to survive due to larval competition.
4. Some pine engravers colonized the logs voluntarily during the experiment. These volunteers settled independently of the original density.
5. The fungus Ophiostoma sp. was present on the logs and may be competing with the pine engravers for limited bark area.
6. Aggregation resulted in a considerable cost to pine engraver reproductive success even at low densities. Thus, it remains perplexing why pine engravers aggregate actively in nature.