No. 556] DEVELOPMENT IN NICOTIAN A 



217 



plants in both F 2 and F 3 and the homozygous normals 

 and abnormals obtained in this manner bred true in F 3 

 and F 4 . Not being satisfied that only one factor repre- 

 sented the difference between the normal and the abnor- 

 mal, I thought that it might be possible, through selection, 

 to secure a normal strain from the abnormal, or at least 

 to modify the unit character, as Castle and his students 

 appear to have done with the hooded pattern in rats. 



Selection work was started by selecting from the cul- 

 tures the most abnormal and the least abnormal plants 

 as seed producers. The work was carried through two 

 generations with no prospect of success and there it re- 

 mains at present. Progeny of the least abnormal plants 

 were as much fasciated and otherwise abnormal as the 

 original parent strain growing beside it. And one could 

 not distinguish the least abnormal from the most ab- 

 normal strain except by the label. So far as the work 

 has progressed, this fasciated strain seems no more amen- 

 able to selection than the cockscomb with which De Vries 

 worked, and of which he said "at present at least there 

 seems not to be any prospect of obtaining a pure atav- 

 istic strain." 18 



From a comparison between the drawing in Gerarde's 

 Herball of 1597 19 and certain woodcuts from old horti- 

 cultural magazines with the plants as they are to-day, it 

 does not appear that much change has taken place in the 

 cockscomb fasciation since its introduction into Europe 

 in 1570. 



The changes in the expression of the comb that gar- 

 deners and florists will maintain have taken place as a re- 

 sult of selection can all be accounted for by the influence 

 of the environmental factor. 



Look planted seeds of very slightly fasciated individ- 

 uals of the F 2 generation of normal X fasciated stem in 

 Pisum. The F 3 plants were almost, if not as much fas- 

 ciated, as the original grandparent strain. 20 



18 De Vries, H., "The Mutation Theory," 2: 519, 1910. 

 "Gerarde, John, "Herball or Generall Historie of Plantes," 1st ed., 

 pp. 323-325, Fig. on p. 323, 1597. "Lock, E. H., loc. cit., p. 106. 



