Summary Comparisons of pyrene set were made between raspberry flowers pollinated with undiluted pollen and others pollinated with pollen diluted with talc, or killed pollen. Pollen dilution reduced set but the reduction was not the same for all maternal parents. It also reduced the rate of fruit ripening, increased the proportion of pyrenes without seed content and reduced the tendency for abortive carpels to develop into small empty pyrenes. Observations of numbers of pollen grains germinating in the styles revealed differences attributable to the maternal parents, the pollen germinating poorest on the parent whose pyrene set was reduced most by pollen dilution. There were also maternal × paternal interaction effects on pollen germination. It is concluded that pollen germination was conditioned by growth substances provided partly by the grains themselves and partly by the styles of the seed parent, and that there were interactions between the two sources. Reduction in pollen concentration affected several aspects of early fruit development, but quantitative differences in the amount of pollen applied did not reduce the adverse effects of using diploid pollen. This suggests that such effects do not arise through direct action of the pollen on the maternal tissues.

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Resum^: ZasammenfassungLinear regression of dry weight of weeds against crop density, together with the use of diversity indices and principal component analysis were used to derive inforniLition about changes in the behaviour of annual weeds over the growing season and in response to a wide range of crop densities in vining peas Pi.sum sativunt L. Using linear regression it was possible lo quantify reductions in weed dry weights per unit increase in crop plant density. The "weed loss" factor was acceptably consistent between experiments. Indices examining richness and evenness showed that numbers of weed species declined with increasing crop density and as the season progressed, but although species evenness became less at successive sampling dates the presence of a pea crop, whatever its density, did not radically alter [he composition ofthe weed flora. Principal component analysis demonstrated that although there was competition wiihin the weed flora, ihe crop did not replace the dominant weed spwcies on high density plots, but reduced growth of all weed species alike. Concurrence entre les mauvaises herhes annuelles et les pois industriels cultires a diverses den.sites: effet.% sur les mauvaises herbesLa regression lineairedu poids sec des mauvaises herbes par rapport a la densite de la culture a ele utilisee. en association a des indices de diversite el a l'analyse en composantes principales. pour obtenir des donnees sur les modifications dans le comportement des mauvai.ses herbes annuelles lout au long de I'epoque de vegetation ainsi que par rapport a une large gamme de densites culturaies des pois industriels (PMH/JI sativum L.). L'emploi de la regression lineaire a permis d'evaluer avec precision les reductions dans le poids sec des adventices par unite d'augmentation de la densite des plantes cultivees, Le facteur'perte due aux adventices' est reste assez constant d'une experience a l'autre, Des indices relatives a la richesse et la repartition florisiiques ont revele que les nombres d'especes adventices diminuaient au cours de la saison et a mesurequ'augmentait la densite de la cullure; mais tout en admeltant que la repartition des especes devienne moins cgale a chaque nouveau prelevement. la presence d'une culture de pois. quelle qu'en fut la densite. n'a point modifie foncierement le cortege florislique. L'analyse en composantes principales a fait voir que. malgre une concurrence parmi les especes adventices. la culture n'u pas rempiacc I'espece dominante sur les parcelles a haute densite culturale. Au contraire. elle a amene une diminution pareille chez toutes les especes adventices. Konkurrenzkrafiverschiedener Dichwn der Erhse (•Pisum salivum L.I gcgeniiher einjahrigen Unkrautern

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Umbilicaria propagulifera (Vainio) Llano is reported as new to Poland. A morphological description is given and its distribution in both southern and northern hemispheres is established. U. vellea var. dendrophora is considered to be a synonym. The chemistry of U. propagulifera is variable. Its affinities within the genus and its possible relationship, as a species pair, with U. cylindrica are discussed.