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The concentration of sugar in the nectars of unprotected flowers of several species was measured and did not reach the high values that would be in equilibrium with the daytime humidities recorded outside the corolla, although the sugar concentration was highly correlated with ambient relative humidity. This paper examines features that maintain low nectar sugar concentrations at low ambient humidities. Post-secretory changes in concentration are influenced to a small extent by nectar composition but depend largely on physico-chemical and microclimatic effects. Factors contributing to the maintenance of steep gradients in water activity between the nectar and the ambient air include corolla morphology, sugar concentration gradients and waterproofing lipid monolayers on the nectar surface. This paper considers the relative importance of such features in relation to the pollination syndrome. A simple technique is described for the measurement of intrafloral relative humidity. [ABSTRACT FROM AUTHOR]

Large numbers of human cells can be reversibly arrested in mitosis by high-pressure nitrous oxide. The optimum schedule for this arrest requires that the high-pressure block be started around midnight to provide a mitotic population that can be released the next morning to progress in synchrony through the next cell cycle. We describe a simple and safe device which can be set up at the end of the day and automatically exposes the cells to high-pressure nitrous oxide overnight.

The paper describes a portable electronic device which automatically records a measure of object play behaviour, by counting the number of contacts made with a play manipulandum. The device is designed for recording a measure of object play in domestic cats, but is readily adaptable for use with other species.