[The question of chemically determined physiological resistence of cultivated plants].

A survey is given of the problems concerning chemically determined resistance in cultivated plants. Leaving aside resistances caused by anatomical and morphological characteristics as well as by immunological reactions and/or by phytoalexines, two main groups of substances, cytostatica (alcaloids acting upon mitoses) and biostatica (acting upon the cell plasm) are discussed in detail. Biostatica are defined as so-called preformed substances developed by the plants themselves and acting additatively and/or cumulatively by building up various levels of resistance towards pests, e.g. by lowering their fertility. In vertebrates (chicks) they proved responsible for direct damages to certain organs as well as for indirect disorders caused during the prenatal and postnatal development of their progenies.The relations between the two groups of chemicals are discussed from the point of view of resistance, considering the role of biostatica and cytostatica during evolution. There is evidence against biostatica being products of immunological reactions.