The studies on the genus Zanthium, of which this is a preliminary account, were begun in the autumn of 1922. An attempt was made to obtain seeds of Xanthium from all part of North America and thus to gain some idea of the distribution of species. It was hoped, also, that a study of the plants, from germination to maturity, would throw some new light on the taxonomy by revealing genetic relationships in the genus. An experimental garden has been devoted exclusively to Xanthium for two summers. In 1923, seeds from 22 different sources in North America, were grown. In 1924, all the seeds planted had been collected in two small areas on opposite shores of the St. Lawrence at Montreal. Small numbers of plants have been grown in the McGill University greenhouse during the winter months of both years. [...]

Stehle, R. (Supervisors)

Lloyd, F. (Supervisors)