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Nothing is more striking to the casual observer than the vast 

 predominance of introduced individuals in the more densely 

 settled areas. Often the native species have been entirely 

 crowded out, and the grass-population over large sections is 

 made up exclusively of immigrants, among which the genera 

 Bromtis and Lolium will show the greatest number of individual 

 representatives. 



The following attempt to group our grass-species ecologically 

 is far from being exhaustive, but may serve to throw a little 

 more light on the general phenomena of distribution. The 

 following associations may be distinguished : 



1. Riparian society, growing on the sand-bars and islands in 

 the Willamette and Santiam Rivers, and along their muddy or 

 gravelly shores, often in very dry soil: Digitaria humifusa, 

 Paspalum distichiim, Panicum harhipulvinatum, Aristida oligan- 

 tha, Agrostis foliosa, Aira capillaris, Eragrostis hypnoides, Poa 

 compressa, Festiica octoflora. 



2. Hydrophyte society, growing only in water or wet ground 

 along streams, borders of ponds &c. : Leersia oryzoides, Alopecurus 

 aristulatus, Agrostis microphylla, A. oregonensis, Deschampsia 

 caespitosa, Poa triflora, PJiragmites communis, Glyceria leptosta- 

 chya, G. occidentalis, G. pauciflora, G. grandis, Beckmannia 

 erucaeformis. 



3. Xerophyte society, found usually only in dry soil, especially 

 on the gravelly prairies: Panicum Scribnerianum, P. pacificum, 

 Stipa Lemmoni, Aira caryophyllea, DantJionia americana, Koeleria 

 cristata, Bromus sterilis, Poa scabrella, Festuca megalura, F. 

 rubra, F. idahoensis, Agropyron tenerum, Elynius glaiicus, Sitanion 

 jubatum. 



4. Silvicole society, generally occurring only in or at. the 

 borders of open woods: Trisetum cernuum, T. canescens, Melica 

 subulata, Bromus vulgaris, B. vulgaris var. eximiiis, Poa Howellii, 

 Festuca occidentalis, F. subulata. 



5. Submontane society, restricted to the wooded lower slopes 

 of the mountains, and not extending out into the valley: Hieroch- 

 loe macrophylla, Agrostis hyemalis, Pleuropogon refractus, Poa 

 nervosa, P. leptocoma. 



