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the original material is sand, mixed with gravel and loam; 

 and the decaying remains of many seasons' growth have spread 

 a layer of humus over all parts except those nearest the river, 

 where an occasional vessel still deposits fresh material. A few 

 belts of crushed obsidian have successfully resisted the inroads 

 of the invaders, and afford access to the center of the tangle. 

 The very large proportion of plants bearing burs or prickles 

 makes the task of the collector far from pleasant. 



In the last two seasons I have made six trips to Linnton, on 

 August 28 and October 9, 1915, and June 17, July 29, September 

 2, and October 14, 1916. I have made notes on all the plants 

 that I have observed, and brought home specimens of all that 

 were unfamiliar. In many cases I have found it impossible, 

 with the limited herbarium and library resources at my com- 

 mand, to determine or even make a guess at their identity. I 

 must express my obligations to the staff of the Gray Herbarium 

 of Harvard University, to Mrs. Agnes Chase, of the U. S. Dept. 

 of Agriculture, and to Mr. Kenneth K. Mackenzie, of New York 

 City, for their kindness in determining these puzzling species. 

 Specimens of practically all the species that have not been 

 heretofore reported from Oregon have been deposited either in 

 the Gray or the National Herbarium. 



The fact that each successive visit has brought to light species 

 not observed on previous visits, convinces me that the following 

 list is far from being complete, and that another season will add 

 materially to the number. Students will observe that while 

 many plants in this list are familiar everywhere, a large propor- 

 tion of the total is made up of species whose occurrence at a point 

 so remote from their original range is deserving of remark. In 

 many cases these unfamiliar visitors are the plants most solidly 

 established, and showing the greatest likelihood of becoming 

 permanent residents. Very few of them, unfortunately, can be 

 regarded as welcome additions to our flora, or as tending in 

 any way to be beneficial. It is fortunate that the region about 

 Linnton is not an agricultural one; otherwise it might be a wise 

 provision on the part of the state to extirpate the entire area. 



In presenting the following list, which is to be regarded as 



