554 Heritable Spiral Torsions. 



The existence of constant intermediate races or ever- 

 sporting varieties exhibiting spiral torsion seems to me 

 to be conchisively demonstrated by the experiments de- 

 scribed. They were found by chance and then easily 

 extracted by isolation, and induced to produce a pro- 

 portion of 30-40% twisted individuals. This result could 

 be made permanent by subsequent cultivation, but could 

 not be increased by a continuation of the selection. 



§ 21. THE SIGx\IFICANCE OF THE ATAVISTS. 



In spite of every attention and in spite of repeated 

 and careful selection spirally twisted races will continue 

 to produce numerotis atavists. These are either decussate 

 individuals of the normal structure of the species, or 

 they have ternary leaf whorls, as is also often seen in 

 twisted individuals above the torsions. 



I propose now to examine more closely the nature 

 of, and especially the mode of, inheritance in these ata- 

 vists, as I have done in the case of the fasciations. The 

 essential point about them is that the atavists do not, as 

 we may express it, depart from the twisted race ; but can 

 be used almost as safely for its continuation, as the 

 twisted individuals.^ 



A fact of the highest importance is that there is no 

 sharp limit between the atavists and the twisted individ- 

 uals. Of course the difference between the tall erect 

 stems and the short stunted anomalous ones is most 

 striking, as our Plate VI shows. It is quite clear that 

 this is not a case of the fluctuating variation of a single 



^ In Stocks the double specimens are sterile, as is well known, 

 and the variety has to be propagated by means of the seeds of the 

 single ones. Under cultivation in the field as a rule about 50% of 

 "single" atavists are produced. 



