July 22, 1921] 



SCIENCE 



73 



patliology. Dr. Robertson has also become a 

 member of the staff of the Mayo Clinic as 

 head of the section on pathologic anatomy. 



Dr. Charles A. Shull, now of the Uni- 

 versity of Kentucky, has been appointed in 

 charge of plant physiology at the University 

 of Chicago, to succeed Dr. Wm. Crocker, who 

 has resigned to become the director of the 

 Thompson Institute for Plant Eesearch at 

 Tonkers, IST. Y. 



Dr. R. G. Hoskins, associate in the Johns 

 Hopkins University, has accepted the position 

 of professor and head of the department of 

 physiology in the Ohio State University. 



At George Washington University Dr. 

 John T. Metcalf, assistant professor of psy- 

 chology, has resigned to accept a call from 

 the University of Vermont as associate profes- 

 sor of psychology, and Mr. F. A. Moss, devel- 

 opment specialist at Camp Dix, N. J., has 

 been appointed to fill the vacancy. 



Dr. Willmm H. Cole has been appointed 

 to the chair of biology at Lake Forest College, 

 to succeed Dr. W. C. Allee. 



Dr. H. M. Dadourian, associate professor 

 of physics at Trinity College, is in charge of 

 the physics department in the absence of 

 Professor H. A. Perkins, who is in Europe on 

 a year's leave of absence. 



At the University of Liverpool Dr. McLean 

 Thompson, of the University of Glasgow, has 

 been appointed to the Holbrook Gaskell chair 

 of botany in succession to Professor E. J. 

 Harvc-y-Gibson, who has resigned. 



DISCUSSION AND CORRESPONDENCE 



THE GEOGRAPHIC DISTRIBUTION OF HYBRIDS 



To THE Editor of Science: In your issue 

 of June 17, 1921, Professor Jeffrey, protesting 

 against the assumption " by systematic botan- 

 ists in this country that natural hybirds be- 

 tween species can only exist within the com- 

 mon range of the parent species," calls to his 

 support cases cited by Kerner von Marilaun 

 in the Pflanzenlehen and elsewhere, saying: 



Perhaps the most interesting example in this 

 connection is the hybrid Nuphar intermedium 



which is a cross between Nuphar luteum and Nu- 

 pJiar pumilium. ... It is capable of extending its 

 latitude northward of the range of both the parent 

 species. 



Nuphar iniermedium is thus parallel with 

 the blackberries which I have discussed else- 

 where and, since Kerner is called into the dis- 

 cussion, it is well to quote his conclusion re- 

 garding Nuphar intermedium.^ 



At the northern extremity of this large area of 

 distribution Nuphar intermedium is more abun- 

 dant than the species from which it is derived; 

 indeed in many places it occurs in their absence, 

 and in fact passes beyond the northern limits of 

 their area of distribution. . . . Nuphar interme- 

 dium subsists independently there, multiplies with- 

 out change of form, and has in fact established 

 itself as a species. 



On the same page Kerner discusses two 

 other cases. Salvia sylvestris and Rhododen- 

 dron intermedium. Where it occurs with 

 Salvia nemorosa and S. pratensis, S. sylvestris 

 is interpreted as a hybrid, but it has extended 

 its range beyond either of the two former and 

 Kerner tells us that 



Its fruits ripen in as large numbers as in the 

 case of 8. nemorosa or S. pratensis, and have been 

 found by experiment to be fertile in a proportion 

 of more than 60 per cent. Salvia sylvestris has 

 therefore scattered itself . . . and manifests all 

 the characteristics essential to our conception of a 



Again, Rhododendron intermedium, when 

 growing with R. ferrugineum and R. hir- 

 sutum, is considered a hybrid between them; 

 but Kerner tells us that, in several areas R. 

 intertnedium dominates the vegetation of the 

 mountain sides, 



develops fruits with fertile seeds, and transmits 

 its characteristics unaltered to its descendants. 

 . . . This form accords in every particular with 

 the requirements demanded of a species, and is 

 quite as much a systematic entity as either B. fer- 

 rugineum or M. hirsutum. 



The eases of Ruhus, which stimulated Pro- 

 fessor Jeffrey's note, are exactly parallel with 

 Nuphar intermedium (specially cited by Jef- 



1 1 quote from Oliver 's translation of ' ' Pflan- 

 zenleben," Vol. 2, pp. 588-590. 



