In his geological explorations of the basin of the Red River of the North through six seasons, Mr. Warren Upham has paid careful attention to the geographic limits and relative abundance of both native and introduced plants. "It has been interesting," he says, "to find there the intermingling and the boundaries of species whose principal homes, or geographic range, lie respectively in the direction of the four cardinal points, east and west, and south and north." After describing this diversified vegetation in detail, the author concludes that besides the greater part of our flora which is of northern origin, coming to us from an ancestral flora that probably in the beginning of the Quaternary period occupied continuous land around the globe in high northern latitudes, the plants of the Red River basin include many species derived, as Gray and Watson have shown for a large portion of the flora of California, the Great Basin, and the southern Rocky Mountain region, from the plateau vegetation of Mexico. By the return of a warmer and drier climate in the southwestern United States, following the Ice age of the North, our cactus species, petalostemons, and onagraceæ, many of our composite, the milkweeds, and many more, have been enabled to spread from their original Southwestern and Mexican home-land, becoming a most important element of the flora of all the plains and prairie region to the Saskatchewan and Red Rivers, and gaining a less numerous representation in the wooded country east to the Atlantic coast. How these Northern and Southwestern floras have become intermingled, the geographic limits of separate species, and the gradual changes observable in the specific characters of some of our plants in passing between distant parts of their range, are themes of sufficient interest to repay the careful observations of amateur botanists in all parts of our country. In these directions important additions to botanic science may be made by many who have neither leisure nor ability for valuable biologic study of plants, but who love the search for wild flowers.