Anderson and Schafer. — Species Hybrids in Aquilegia. 645 



recombination, such, for instance, as is responsible for ' atavism ' in crosses 

 between breeds of domestic animals. But A. ecalcarata, though certainly 

 more ' primitive' in its characters than A. vulgaris, is quite as recessive to 

 A. vulgaris as are the ' advanced ' American long-spurred species. 



Z.6-4.0 



k 



\2.l-2.5 

 •1- 16-20 

 \l.l-l.5 

 \ .6-f.O 



0.-.5 



Cross Nf/ 2 3^5678 



Fig. 4. Similar to Fig. 3, but giving the ratio spur length/lamina width. 



It is not impossible that the whole problem is a more purely physio- 

 logical one than might have been expected. It may be that the nuclear 

 substances which produce medium spurs and wide laminae are more effec- 

 tive when diluted than those which produce long spurs and long laminae. 

 In that case we are down to the physiological growth relationships which 

 have limited in a broad way the directions of evolution within the genus. 



The authors wish to thank Miss Irma Andersson-Kotto, who provided 

 the nucleus of the material in 1937. 



Part of the work reported upon in the above paper was performed wh ile 

 the senior author was a fellow of the National Research Council, to which 

 due acknowledgement is made. 



Summary. 



Preliminary studies indicate that species hybrids in the genus Aquilegia 

 tend to resemble A. vulgaris, even where that species is not one of the 

 parents. 



