554 Heritable Spiral Torsions. 
The existence of constant intermediate races or ever- 
sporting varieties exhibiting spiral torsion seems to me 
to be conclusively 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 SIGNIFICANCE OF THE ATAV1STS. 
In spite of every attention and in spite of repeated 
and careful selection spirally twisted races will continue 
to produce numerous 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. 1 
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 
1 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. 
