The Origin of Clirysatithcmum Scgctiim Plcniun. 165 



reasons. In botanical gardens, too, both sorts are often 

 grown together; and, frequently, simply under the name 

 of C scgetiim. 



This mixed asseml)lage gives rise to a dimorphic 

 curve ;-^ but the two groups of individuals which com- 

 pose it can easily be isolated by selection. Then the 

 C. scgeUim grandiflonun proves to have a mean of 21 

 ligulate florets, around which variation practically takes 

 place in the same way as in the 13-rayed race (i. e., the 

 wild species), except that it has a tendency to multiply 

 the number of rays beyond the limits of a normal Quete- 

 let's curve ; a fact which indicates discontinuous varia- 

 tion.^ 



This slight indication was the starting point for my 

 experiment. In 1897 I chose a seed-parent with 34 rays 

 for the 1898 crop, and reached 49 rays.^ Proceeding 

 in the same way I reached 67 in 1899 and about 90 in 

 1900 in the best inflorescences. Up till 1899 the ligulate 

 florets only appeared in the circumference, the disc con- 

 sisting solely of tubular florets. In this year, however, 

 there appeared 2 or 3 ligulate florets in the midst of the 

 disc of a few flow^rheads on a single plant. This was 

 the first indication of the double race. Therefore I only 

 sowed the seeds of this one plant in 1900, and from that 

 the race was fully developed (Plate II). Apart of course 

 from eliminating the possible effects of crossing, it needed 

 no further selection ; a too rigid selection was moreover 



^ Eine ::weigipfclige Van'ationscurve, Archiv fiir Entvvickelungs- 

 mechanik der Organismen, Leipsic, 1895, p. 52. 



^Compare the half curves (p. 26) and the note on page 29. See 

 also Uchcr halhc Galton-Curven als Zeichcn discontimiirUcher J'aria- 

 Hon. Berichte d. deutschen hot. Gesellschaft, Vol. XT I, p. 197. 



^ Uchcr Cun'cnsclccfion bei Chrysanthemum scgctum. Same jour- 

 nal, 1899, Vol. XVTI. p. 84. 



