No effect of weak magnetic fields on seedlings growth of Triticum. No effect of multiple intensities of -4, -1, 0, 1, 4, 6 times the geomagnetic field on the growth ofTriticumseedlings, measured as length, fresh and dry weight, has been found. The experiments were carried out in darkness at 20°C, according to an experimental design including 2196 seedlings placed within the 6 fields with 2 orientations of the embryos (North- and South-wards) and two replicates at the same time. All treatments have been repeated 6 times in 6 different locations. In spite of the statistical significance of the weak magnetic fields «effects» on plants, found from previous researchers, it is very probable that these «effects» are only casual; the results are contradictory, particularly those on the directional «effects»; often the total number of plants and of replicates (sometimes only one) is very low and the environmental conditions are not controlled. Care must be taken in interpreting the results of the probability tests: in analyzing weak effects on these materials the tests have a limited strength and this may produce pseudoeffects, i.e. «probabilistic elaboration effects». The tests easily lose their meaning when they are notstrictlyused according to the theorical conditions, which may not be easily realized. At high intensities no definite responses curves to the intensity and to the direction of the magnetic vector are available. Teratological, pathological, inhibiting as promoting effects on plants growth and development have been recorded. The strong magnetic fields action shows some analogies with that of the ionizing radiations, for their aspecific, casual and disorganizing effects on the physiological processes.