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Oxford OX5 lPF, UK. Summary. A project was set up by the Nigerian government to study the ecology and biology of Eupatoriurn odoraturn and the possibility of biological control. Results of experiments with Gmelina arborea showed that E. odoraturn has very little effect on the establishment of Gmelina. Further experiments to test the interactions of Terminalis superba and lmperata cylindrica with E. odoraturn are being carried out. Work on seed biology shows that there seems to be l i t t l e seed dormancy and the seed does not survive in the soil for long. Soil conditions play an important part in E. odoratum establishment, seedlings growing more readily in sandy than in clay-loam soil. Latvae of the moth Arnmalo insdata Walk. provide the best possibility for biological control. Trials with the seed-eating beetle &ion brunneonigrurn B.B. are still in progress.Applications of either 2.4.5-T or 2.4-D a t 2 kg/ha killed only smaller plants.A mixture of 0.4 kg picloram and 1.6 kg 2.4-0 aminelha was very effective. Further experiments showed that a total dose of this mixture of only 1.0 kglha was still effective. Picloram, however, persisted in the soil for seven months when applied a t 2 kglha. Whilst 2.4-D is less persistant, the stage of weed growth a t which it is applied is far more critical and more trouble can be expected from subsequent seedling regrowth. Altrazine and diuron applied as foliage sprays at 5 kglha were effective.

Summary The germination of U. europaeus seed was investigated at temperatures between 4 and 40°C on a thermal gradient bar. At constant temperature the germination rate increased linearly with temperature from a minimum near 0°C to an optimum at 18°C and then decreased to a maximum at 26°C. At still higher temperatures seeds became imbibed but only germinated when transferred to cooler conditions. Above 35°C viability was lost. The rate of imbibition prior to germination increased with temperature over the whole range. Germination was not increased either by a light treatment or by potassium nitrate. Germination was not stimulated by a wide range of alternating temperature regimes and at mean temperatures below the optimum the germination rate could be adequately predicted from a formula based on performance at constant temperature. At higher temperatures the observed rates became progressively slower than predicted. Seeds from three different sources were tested, all showing similar relationships between germination rate and temperature but differing in the proportion of hard seed. The proportion was least with seed extracted from the soil, intermediate with a collection from the surface and greatest from pods. The findings are discussed in relation to germination in the field following clearing of gorse thicket.

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Summary: Competiton between seedlings of gorse (Ulex europaeus L.) and perennial ryegrass (Lolium perenne L cv. Grasslands Nui) was studied in a replacement series experiment under glasshouse conditions. Without cutting, the shoot growth of gorse in monoculture exceeded that of ryegrass over 22 weeks but was reduced more by competition from ryegrass than the grass growth was reduced by competition from gorse. The root system of gorse was small compared with that of ryegrass and was further reduced by competition. Cutting three times at 2 or 4 cm reduced the total growth of both species and gorse was affected more than ryegrass. With grass, however, the ‘growth between succeeding cuts declined faster than that of gorse and in the final harvest period, gorse in monoculture oulyielded ryegrass. The relative crowding coefficients of gorse were low compared with those of ryegrass and their products consistently exceeded 1.0. The results are discussed in relation to lirmiting seedling establishment of gorse in the field.