No. 586] 



ANNUAL SUNFLOWERS 



621 



incisions, and also some narrow supplementary rays; 

 Boulder, Colorado, August 8, W. P. Cockerell). 



Double Rows. — The disc remaining normal, the rays 

 may be in two rows, indicating an approach to a type re- 

 sembling the star dahlias. 



Color. — The yellow may be of various shades from 

 deep orange to very pale, approaching white. This has 

 already been discussed in Science, August 21, 1914, pp. 

 283-285. It may be possible eventually to get a pure 

 white. Dr. Church (in litt.) refers to a white form as 

 having been mentioned long ago by Hernandez. There is- 

 also the development of the soluble (anthocyanin) red 

 pigment, giving us the chestnut red and wine red vari- 

 eties. 



Conclusions 



It is impossible at the present time to give all the evi- 

 dence on which opinions have been formed, but such facts 

 as are reported above, and others, seem to suggest the 

 following generalizations : 



1. The number of genes or determiners in Helianthus is 

 not infinitely great; it is probably very much less than 

 exists in most animals, and the study of the processes of 

 heredity is relatively simple. 



2. In the history of the sunflowers of the H. annuus 

 group, there have been few really new developments. 

 Species which seem very distinct prove on examination 

 to have few special characters of their own. 



3. It is quite common for variations to arise, in wild 

 and cultivated plants, which appear to break the type, 

 and initiate something altogether new. "When, however,, 

 we begin to gather data on the variation of the Composite, 

 we find that practically all these " new " variations re- 

 peat themseles in various species, and at various times r 

 indicating that they represent deep-seated common tend- 

 encies. Their occurrence among wild plants shows that 

 they are not necessarily connected in any way with culti- 

 vation, and it is equally evident that they need not indi- 



