Rare Spiral Torsions. 541 



in small numbers. Sometimes these were confined to the 

 vegetative parts, but sometimes the calyx, together with 

 the upper pair of leaves, was transformed into an open 

 spiral (Fig. 128). 



In order to determine the intensity of inheritance of 

 this anomaly in such cases, I have conducted an experi- 

 ment with Dipsacus laciniatus. This plant was of pecu- 

 liar interest to me because it belonged to a genus which 

 has been known for a long time to produce fine spiral 

 torsions and to which also the Dipsacus syk'cstris be- 

 longs, from which I have been able to isolate an ever- 

 sporting variety which produces this anomaly in abun- 

 dance. In Dipsacus laciniatus, on the other hand, the 

 attempt to effect a similar isolation was unsuccessful. In 

 this case an intermediate race was not present, but only 

 a half race; for in spite of extensive cultures for two 

 generations no more than slight local torsions were ob- 

 tained. 



A plant of Dipsacus laciniatus which I had seen in 

 full bloom in the botanical garden at Groningen formed 

 the starting point of this experiment. It was over two 

 meters high with a perfectly straight stem which, how- 

 ever, had a little group of spirally arranged leaves at 

 one of the upper nodes and here exhibited local twisting. 

 Prof. J. W. Moll kindly sent me seeds of this plant. 

 From these I grew in the two following years 400 plants 

 on a bed of about 16 square meters, that is about 25 per 

 square meter, which may be regarded as giving am])le 

 room. The sowing took place in the beginning of April. 

 In the summer of 1897 all the stems became straight; 

 not a single one was twisted, as in Dipsacus syh'cstris 

 (Fig. 123, p. 529). Moreover, the arrangement of the 

 leaves was decussate in all of them. Slight abnormal- 



