560 Heritable Spiral Torsions. 



ting tlie long stalk of the terminal inflorescence, which 

 is always i)resent, I obtained the following series. 



PLANTS WITHOUT WITH 0-6 STRAIGHT INTER- 

 TORSION NODES ABOVE THE TORSION 



Straight internodes 6 5 4 3 2 1 



Individuals 900 2 3 1 2 40 200 148 



The curve constructed from these figures is obviously 

 one with two peaks, and essentially the same as the cor- 

 responding curve for fasciations seen in Fig. 118 (p.521). 

 Torsions with two, with one, and without any straight 

 internodes above the torsions are far the commonest. 

 Smaller torsions only occurred in nine cases among 1295, 

 that is less than 1% of all the individuals, or in about 

 2% of the twisted individuals. I repeated the same ex- 

 aminations in 1902; the intermediate forms wxre some- 

 what more numerous and reached a proportion of about 

 7% in 492 individuals. The form of the curve, was, 

 how^ever, not essentially modified. 



In order to determine the hereditary coefficients of 

 the atavists I instituted an experiment in the eighth and 

 ninth generation of my race. In July 1900, I had some 

 highly twisted plants, some completely decussate ones, 

 and some with ternarv wdiorls only, on the same bed. 

 Before the flowering period I reduced the inflorescences 

 to the required number and afterwards insured pure fer- 

 tilization in the following w^ay. All the inflorescences 

 were enclosed in parchment bags, and the bags were 

 taken off the individuals falling into one group, for sev- 

 eral hours one day out of three for each group. The 

 humble bees flying about could thus fertilize only twisted 

 individuals on some days, on others only decussate, and 

 on still others only ternarv ones. This practice was 

 continued until all the flowers Avere gone. The seeds 



