24 



The depth of the involucre remained constant for all the forms 

 collected. 



The notes here presented are but inadequate observations. 

 They suggest the desirability of conducting genetical studies in 

 this genus which as in the case of the mutating Oenotheras con- 

 sist of forms growing far from their place of origin. 



Extensive exiperiments might solve the problem as to whether 

 in these elongated receptacles we have mutating characters or re- 

 versions. The resulting spike-like cluster characteristic of more 

 primitive plants might indicate the latter interpretations as the 

 more probable. Jost states on page 395 of his work on Plant 

 Physiologic tf " New characters, that is mutations, behave the 

 same as reversions." 



It is in the genus Achillea that we also have the oft-quoted ex- 

 amples of species mutually excluding each other from calcareous 

 and siliciferous soils. Schimper states in Plant Geography ,t 

 page 105, that Achillea millefolium will grow equally well in 

 either kind of soil wdiile A. inoschata is an inhabitant of silicif- 

 erous soil, excluding A. at rata which prefers calcareous soils. It 

 would be of interest to determine the lengths of the receptacles of 

 the plants growing in these different kinds of soils and the influ- 

 ence if any of change of soil in modifying the lengths of the re- 

 ceptacle. It is possible also that seasonal conditions may be im- 

 portant factors in the appearance of these interesting plants. 



Hunter College, 

 New York City 



ADDITIONS TO THE FLORA OF WESTERN OREGON 



DURING 1920 



By James C. Nelson 



Although the writer did not find it possible to collect very ex- 

 tensively during the past season, the introduction of foreign 

 plants into Western Oregon seems to have gone on unchecked. 



t Jost, Liidwig, Lectures on Plant Physiology, 1907, trans, by Gibson. 

 t Schimper, A. F. W., Plant Geography upon a Physiological Basis, 1903. 

 trans, by Fisher. 



