1.- In attempts to obtain intergeneric crosses, pollen of 65 spedes was tested on stigmas of Datura stramonium (Jimson Weed).
2.- Pollen of the solanaceous plants showed much more successful germination than that of the other families (93% against 43%).
3.- On the average, the Solanaceae showed a faster tube growth tube the rest of the families (10,8 mm against 5 mm).
4.- Most oí the pollen tubes tested showed a decrease of speed as they approached the ovary.
5.- The fact that pollen of species belonging to distant related groups germinated on the stigma of Datura stramonium seems to mean that pollen germination is not determined exclusively by taxonomic relashionships.