Anthers of barley have been cultivated at the uninucleate stage on several artificial media and the evolution of the microspores has been followed during the first days. The presence of an auxin is necessary for the cell proliferation and several pretreatments increased the frequency and the precocity of the divisions: the best is a storage of two days at 3°C before inoculation. An important part of the polyploidy in the tissues in the consequence of endomitosis in the microspore nuclei. The proportion of polyploidy rises in older calli but some tissues remain haploid.