CHROMOSOME NUMBERS IN COMPOSITAE V. ASTEREAE II.

Reports of 100 new chromosome counts are made for the tribe Astereae of Compositae, mostly based on determinations of meiotic material, including first counts for 9 genera and 53 species. Counts are now available for 58 of the approximately 100–120 genera and 431 of the approximately 2000 species in the tribe. Comparisons are made between chromosome number and habit and also between chromosome number and geographical distribution. Species and genera with a basic number of x = 9 are the most abundant. Within different phyletic lines x = 9 is also the most abundant number. On the other hand, many species with x = 4 and 5, belonging to a number of small, largely annual genera, are concentrated in southwestern North America. The low chromosome number in these plants is probably correlated with the dry habitat they occupy, and is most likely a specialized condition.     

ANTIGENS IN EGGS AND DEVELOPMENTAL STAGES OF THE SEA URCHIN : I. Immunological and Physicochemical Properties

A number of antigens in unfertilized eggs and embryos of the sea urchin Paracentrotus lividus were characterized with respect to both immunological and physicochemical properties. Experiments involved single diffusion in agar (Oudin technique) combined with mutual dilution, serial dilution, and heating of antigenic extracts, as well as immunoelectrophoresis with normal and heated extracts and agar electrophoresis followed by staining of the antigenic spots with protein specific dyes. The gradual transition in migration rates of bands of precipitates in Oudin tubes following mutual dilution of either extracts or antisera allowed the identification of 6 immunologically identical antigens in eggs and embryonic stages. Similarities with respect to diffusion coefficients, sensitivity to heat, electrophoretic mobility, and reaction to protein specific dyes indicated that the antigens in extracts of eggs and various developmental stages also had certain physicochemical properties in common. Such knowledge is of importance for an understanding of antigenic changes occurring during ontogenesis.     

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Autoradiographies de Coupes d'os compact après marquage aux isotopes in vitro

Résumé Etude qualitative et quantitative du marquage in vitro de coupes d'os compact. Détermination du rôle joué par les processus de diffusion, d'adsorption et d'échange dans ces phénomènes.

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Zusammenfassung Qualitative und quantitative Studie der in vitro-Markierung von Schliffen aus Knochen-Compacta. Bestimmung der Rolle der Diffusions-, Adsorptions- und Austauschprozesse für diese Vorgänge.

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La partie expérimentale de ce travail a pu être réalisée grâce à des subsides fournis par l'European Office of the Air Research and Development Command [contrat n^o AF 61 (514) 1175], par l'Institut Interuniversitaire Belge des Sciences Nucléaires, et par la Commission pour la Science Atomique du Fonds National Suisse de la Recherche Scientifique.