In different plant species maternal factors influence the germinability of seeds. It can also be modified by environmental factors occurring during development and maturation. Achenes ofMatricaria maritima subsp. inodora were collected in summer 1995. Some of seeds were tested under controlled conditions in autumn the same year. The other part of seeds was buried. After 6-month stratification in the soil, diaspores were tested under the same conditions as a sample examined in autumn. It was shown a difference in germination, which was dependent on stage ofmaturation seed, position of inflorescence on the mother plant and the position of seeds in inflorescence. It was observed that seeds germinated much better in autumn than diaspores stored in the soil during winter.

The effect of density on individual and population fertility, and selected morphometric characters (height, number of: ramifications, generative branches, inflorescences and leaves) of Echinochloa o-us-gaili plants was studied in a glasshouse. A decrease in individual fertility was observed in all density variants examined, but it did not result in a decrease in population fertility per unit of area. In response to worse developmental conditions there appeared plants characterized by reduced height and simplified external conformation.

The aim of the study was to investigate the effect of some different environmental conditions prevailing during the development and ripening of Echinochloa crus-galli diaspores on their germination. Some seeds were tested in the autumn the same year, whereas others were divided into two groups: dispersed seedsand seeds within the inflorescence. Then the seeds of both groups were buried. After eight-month stratification in the soil, the diaspores were tested under the same conditions as the samples examined in the autumn. The seeds tested in the spring germinated faster than those tested in the autumn. Also the germination capacity of barnyard grass caryopses examined in the summer was almost twofold higher than the germination capacity of those examined in the autumn. Both autumn and spring tests revealed that the harvest time affected germination. The seeds obtained in the second half of August and at the beginning of September (in the middle of the growing season) were characterized by a higher germination capacity than the caryopses collected at the beginning and the end of the reproduction period. The results show that the germination capacity and rate were not influenced by the place of origin, habitat conditions and accompanying plants. It was found in spring tests that germination depended on the kind of dissemination unit stored in the soil. After eight-month soil stratification, dispersed caryopses germinated by approx. 20% better than those stored with a part of the inflorescence.