The tepals of cut flowers of Tulipa hybrida cv. Golden Apeldoorn and Tulipa kaufmanniana cv. Shakespeare abscise 3–4 days after harvest. The weakening of the abscission zones is accompanied by cell wall breakdown and the separation of 3–4 rows of intact cells at the base of the tepal. During senescence, there is no ethylene climacteric and ethylene production rates remain low, between 0.07 and 0.4 nl g−1 fresh weight h−1. Adding 3–5 μl l−1 ethylene slightly accelerated the weakening of the abscission zones but had no effect on the time of first abscission. Neither 0.5 mM silver thiosulphate nor 5 mM aminoethoxyvinylglycine delayed the time to abscission. It is concluded that tulip tepal fall does not involve primary regulation by ethylene, unlike the majority of other abscission systems that have been studied.

The avian strain P-1059 of Pasteurella multocida was grown on blood agar (BA), on dextrose-starch agar (DSA), or in Heddleston's hydrogen sulfide test broth. Cells were examined for the presence of pili using electron microscopy after staining with phosphotungstic acid, and they were examined for capsule after ruthenium red staining. Pili were found on the capsulated iridescent type, P-1059I, and on two non-capsulated variants, the blue, P-1059B, and the gray, P-1059G. Many cells grown on BA were heavily piliated. In contrast, fewer cells grown on DSA had pili, and piliation was only slight to moderate. The P-1059I, P-1059B, and P-1059G produced pellicles when grown on broth medium. Pili were found on the circumference of the cells grown on either agar or broth medium. Occasionally a pilus connecting two cells was seen on cells cultured in broth. Cultivation of the P-1059I on DSA containing the iron-chelating agent alpha,alpha'-bipyridyl produced a non-capsulated blue variant. The non-capsulated variant reverted to P-1059I when grown on BA but did not revert when grown on DSA.

Blood agar, prepared with Trypticase (BBL Microbiology Systems, Cockeysville, Md.) soy agar and 5% defibrinated bovine blood, is used for testing the potency of live Pasteurella multocida and Pasteurella haemolytica vaccines, but its potential for variation makes it undesirable to use in a standard assay method. Tests done with RPMI 1640 and Trypticase soy medium indicated that the benefits obtained by adding defibrinated blood to the Trypticase soy agar medium were more likely due to neutralization of toxic components than to the presence of transferrin or iron as growth factors. Reduction of toxic components in the Trypticase soy agar medium was accomplished by replacing agar with agarose and by autoclaving glucose as a separate solution to produce the replacement medium. The replacement medium was prepared by autoclaving three separate solutions-Trypticase soy broth without glucose; glucose; and agarose-cooling to 55°C, and mixing and then pouring the mixtures into petri dishes. The growth obtained with this medium as judged by determination of the number of CFU and the colony sizes of P. multocida or P. haemolytica was equal to or better than those obtained with blood agar.