One of the interesting parts dealing with geographical botany is the question of the distribution of plants over the earth's surface, where man has played an important part. Many changes have occurred in the character of our North American flora since it has been occupied by man. In many cases it has become quite impossible to tell when and where plants were first introduced. We have, it is true, in some cases records when plants were introduced, but in the vast majority of cases there were no records at hand. Early collectors in many cases simply mentioned vague localities with dates, but say nothing as to whether the plants are indigenous or introduced. Papers dealing with the spread of certain weeds have been made by several investigators in both Europe and America. Franz Buchenau has carefully traced the spread of Leersia oryzoides. L. H. Dewey that of Salsola kali, var. Tragus.
Proceedings of the Iowa Academy of Sciences
©1894 Iowa Academy of Science, Inc.
Pammel, L. H.
"Distribution of Some Weeds in the United States, Especially Iva xanthifolia, Lactuca scariola, Solanum corolineum and Solanum rostratum,"
Proceedings of the Iowa Academy of Science, 2(1), 103-127.
Available at: https://scholarworks.uni.edu/pias/vol2/iss1/27