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 w^hich produce the anomaly abun- 

 dantly have been very rare hitherto. They will be de- 

 scribed in the following section (§ 19). 



Fig. 122. Valeriana officinalis. xA-ii entire plant the stem of 

 which attained the height of lO 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 



