Patterns of pollen removal and deposition in tristylous Pontederia cordata L. (Pontederiaceae)

In tristylous Pontederia cordata (Pontederiaceae), conspicuous differences in the size of pollen grains and discrete variation in the length of reproductive organs provide a suitable experimental system for the study of fine-scale pollination events. At a population of P. cordata at Pothole Lake, Ontario, the majority of flowers are visited by bumble bees which remove on average 45% of the pollen during single visits to previously unvisited flowers. The amount and proportion of pollen removed are significantly different among floral morphs and stamen levels. Deposition of the three pollen types on the bodies of Bombus spp., Apis mellifera and Melissodes apicata is non-random: large- and medium-size pollen tends to remain in greatest concentrations where it is initially deposited, whereas small-size pollen is displaced from the proboscis to more posterior body parts, probably as a result of grooming activities. Stigmatic pollen loads of individual flowers following single bumble bee visits indicate that the mid-styled morph captures the largest total pollen load, and the short-styled morph the smallest. The largest proportion of compatible pollen grains is deposited on stigmas of the long-styled morph. Pollen load data from "single visit" flowers is in general agreement with previously published population surveys involving multiply-visited flowers.     

Induction of the Feline Oncornavirus Associated Cell Membrane Antigen in Human Cells

BY N-terminal amino-acid sequence analysis, Glenner et al.¹ have shown that amyloid fibrils are very similar to the variable part of an immunoglobulin kappa light chain (Bence-Jones protein Ker) and they suggested that amyloid is constituted by immunoglobulin light chains.     

The Effect of Molybdenum upon the Nitrogen Metabolism of Anabaena cylindrica: I. A Study of the Molybdenum Requirement for Nitrogen Fixation and for Nitrate and Ammonia Assimilation

The effect of molybdenum concentration upon the growth of Anabaenacylindrica is studied. Within the range of molybdenum concentrationthat it was found possible to achieve by the methods described,the element does not affect growth on ammonium chloride, butit is required for healthy growth on nitrate or gaseous nitrogen,the optimal concentrations being about 0·075 and 0·20p.p.m., respectively. Molybdenum appears to be unnecessary fornitrate uptake.     

Effects of cold on nest-building by wild and domestic mice, Mus musculus L.

Nest-building by male and virgin female wild and laboratory mice kept at a temperature of 2^o C was compared with that of controls kept at 23^o C. The amount of cotton wool pulled into the cage was recorded over 24 hours. Nest quality was also assessed. The tests of nest-building were conducted in both cold and warm environments. Cotton pulling was usually at a lower rate in the cold environment, but there was no corresponding decrement in final nest quality. Previous experience in the cold, compared with absence of such experience, resulted in higher scores by wild mice tested in either environment, and by laboratory mice tested in the cold environment. Wild mice that built high quality nests used less cotton wool in the cold than in the warm environment. The tendency for wild mice to pull more cotton wool and build better nests than laboratory mice was more pronounced among cold-treated animals. Differences in body weight did not account for the differences between wild and laboratory mice.
In further experiments nest-building was observed over 16 days. In the cold environment there was an initial depression of nest-building by both wild and laboratory mice, followed by a steady improvement over 6 days.
Both males and virgin females sometimes made well constructed nests even in the warm environment. In the cold environment the effect of previous cold-exposure on wild mice was the rapid construction of a good nest.