names, special symbols are employed in the list of vascular plants 

 here included. 



The numbers in the columns I-VIII indicate the abundance of 

 the species. This can be indicated in a general way only as it 

 varies in different parts of the same area, the accident of distri- 

 bution playing an important part ; and it also varies in different 

 years. The following numbers are employed : 



1 — Denotes locally dominant species. They may be scattered 

 in other parts of the territory. 



2 — Denotes principal species — those iwhich form a conspic- 

 uous part of the flora but do not dominate. 



3 — Marks species which are quite generally distributed in a 

 given area, but do not ordinarily form a conspicuous part of the 

 flora. These are the fairly common scattered species. 



4 — For the rare species, whose occurrence is exceptional, and 

 often quite local. 



5 — For very rare species. 



The letter following the name of the plant in the list refers to 

 one of the following groups : 



a — The most characteristic plants of the prairie, — those most 

 widely distributed in the region, as well as elsewhere on prairies. 

 They are by no means uniformly distributed, but are everywhere 

 characteristic of the prairies. 



b — ' The species usually found only in very dry places, on 

 gravelly ridges, etc. These are the extreme xerophytes of our 

 region, and are chiefly western in distribution. 



c — The species which are more frequently found in rather 

 moist, open places, or sometimes habitually occur only on moist 

 grounds and only exceptionally on the prairie. 



d — The species which prefer the open borders of thickets, and 

 which usually extend out over the prairie chiefly in the vicinity 

 of such borders. 



e — Plants which are usually, or always, found upon sandy 

 areas (other than moist beaches), but always associated with the 

 dominating prairie vegetation. 



f — Species introduced, or occurring as weeds, but which are 

 quite well established even on unbroken prairie. 



The Roman numerals which head the columns refer to local- 

 ities as follows: 



I — A group of gravelly knobs and ridges including the Look- 



28 



