528 
Heritable Spiral Torsions. 
only a small proportion of the plants repeat the anomaly, 
even when the seeds have been saved on the most highly 
modified stems. Races which produce the anomaly abun- 
dantly have been very rare hitherto. They will be de- 
scribed in the following section ( 19). 
Fig. 122. Valeriana ofKcinalis. An entire plant the stem of 
which attained the height of 10 centimeters only. Photo- 
graphed from life in June 1900. Disposition of the leaves 
spiral below, unilateral above. 
In consequence of this rarity the belief prevailed, 
up till about 10 years ago, that these torsions were not 
heritable. The general view was that they were induced 
by special external influences which operated immediately 
upon the individual every time the anomaly arose. At that 
time the experiments which I had made with a twisted 
