66 IVyoming' Experiment Station. 



in common than they have of forms that are distinct. 

 While my collection lists show much that is different, I 

 firmly believe that the difference is due mainly to the 

 season in which each was collected. I am confirmed in 

 this by an examination of the lists given in Dr. J. M. 

 Coulter's report on the Botany of the Hayden U. S. Geo- 

 logical Survey, 1872. These lists comprise those col- 

 lected, I. On both slopes; 2. Only on the eastern slope, 

 and 3. Only on the western slope. Those of the last 

 list were collected in the earlier part of the season, and a 

 remarkable number are the same as those of my list for 

 the eastern slope during the same months. Different 

 localities and seasons yield different results, but complete 

 collections would reveal no abrupt transitions; Iowa and 

 Utah, for instance, have different floras, but any fifty or 

 one hundred miles between, even at the summit of the 

 Rockies, will show only the most gradual substitutions. 

 One form disappears, a new one appears, but this occuis 

 with a change of locality in any direction. On the plains 

 of the Platte and its tributaries Cleome integrifolia only is 

 found, while on Wind River and its tributaries Cleome lutea 

 is the only form. 



INTRODUCED PLANTS. 



By introduced plants reference is made only to such 

 as grow without cultivation. Most of them may properly 

 be called "Weeds." This is an ever-growing list and 

 will soon include a large part of those familiar to the 

 eastern farmer. The extension of our agricultural inter- 

 ests of course includes the importation of seed, and rarely 

 is any kind of seed free from weed seeds. Some of our 

 weeds, however, are native plants and thrive immensely 



