1916] Harper, — An environmental Factor for Primus 201 



three conditions, (1) labile, (2) active, (3) inactive; that, e. g., the 

 nanella pangen or factor for tallness is labile in Lamarckiana since 

 that species can give rise to nanetta through a mutation, while it is 

 only active in rubrinervis since the latter can not give rise to nanetta. 

 In nanella it is considered inactive rather than absent. Correlated 

 with this is the fact that, as we have seen above, Lamarckiana X 

 nanella splits off dwarfs in F b while rubrinervis X nanella splits them 

 off in Mendelian fashion, i. e., in F 2 . 



Instead of the impossible and self-contradictory assumptions 

 regarding degeneration of certain classes of germ cells or zygotes in 

 the various crosses, DeVries made the one assumption that in the 

 zygotes of, e. g., Lamarckiana X nanella either one or the other form 

 or condition obtains ascendency, to the complete exclusion of the other 

 form in later generations. This view is at least self -consistent, which 

 cannot be said of the Mendelian "explanation." If any Mendelian 

 can suggest an alternative explanation which avoids the pitfalls 

 pointed out above, we shall be glad to see it. We have shown at any 

 rate that in the particular group of crosses considered above, the 

 attempt to hide behind sterility as a means of offering a Mendelian 

 explanation only leads to difficulties. So far as we can see, the Men- 

 delian explanation fails hopelessly in all these cases and in others as 

 well. 



It will be time enough to consider East's other objections to the 

 point of view of my book when the points discussed above have been 

 cleared up. 



AN OVERLOOKED ENVIRONMENTAL FACTOR FOR 

 SPECIES OF PRUNUS. 



Roland M. Harper. 



In the March number of Rhodora, pages 00-70, Mr. Bayard Long 

 reports finding Primus cuneata on the southeast side of a creek or 

 small river in the pine-barrens of Ocean County, New Jersey, especially 

 on a gravelly railroad embankment in the creek swamp; and he dis- 

 cusses at some length the question of whether it can be native there, 

 in view of the fact that no other stations for it are known within 

 many miles. 



