MAN AS A MAKER OF NEW PLANTS — ANDERSON 



467 



Figure 3. 



Figures 1, 2, and 3. — A diagrammatic and greatly simplified demonstration of the extent 

 to which the domestication of the sunflower as a cultivated plant and its development as a 

 weed are processes rather than events. Data from Heiser (1949, 1951) and personal com- 

 munications, and from my own observations. The history of the cultivated sunflower, 

 complicated though it is shown to be, will be simpler than that of most cultivated plants 

 when these histories have been worked out in accurate and documented detail. Various 

 complications haye been ignored altogether to keep the diagram intelligible, as, for instance, 

 the continuing intercrossing between the "camp-follower" weed and the cultivated orna- 

 mental and field-crop sunflowers. 



Figure 1. — Annual species of North American sunflowers as presumed to have existed in 

 prehuman times: (/) Helianthus exilis, a highly localized endemic in the serpentine areas 

 of California; (2) H. petiolaris on bare sandy areas in the western Great Plains; (3) H. annuus 

 in playas and other raw-soil habitats of the southwestern deserts; (4) H. argophyllus on the 

 sands of the Texas coastal plain; and (5) H. debilis in Florida and Texas. 



Figure 2. — Hypothetical origin of the North American sunflower as a weed and as a 

 cultivated annual in pre-Columbian times. In the areas where annuus and petiolaris had 

 begun to introgress, this process is being unconsciously accelerated by the activities of early 

 man. 



Figure 3. — Spread of annual species of North American sunflowers in modern times. In 

 the Great Plains extensive introgression of annuus and petiolaris produced the Great Plains 

 race of H'lianthus annuus, which has spread eastward through the prairies as a somewhat 

 weedy native. The camp-follower weed (sometimes mixed with Great Plains annuus) has 

 spread as a weed throughout the East and to irrigated lands in the West. In California, 

 by extensive and continuing introgression with exilis, it has created the semiweedy H. 

 bolanderi, which is still actively spreading. Similarly on the sands of the Texas coast and 

 the Carrizo ridge, H. argophyllus is introgressing actively with H. annuus to produce weedier 

 strains. Over an even wider area in Texas extensive introgression of annuus, petiolaris, 

 and cucumerifolius is producing a coastal-plain weed sunflower which is actively spreading 

 along the coast. In spots it has already reached the North Carolina coastal plain. Even- 

 tually this will react actively with H. debilis var. debilis, breeding a superweed for the Ameri- 

 can Southeast but, fortunately, a not unattractive one. The Texas and California phenom- 

 ena have already been documented by Heiser (1949, 1951), and research on other facets 

 of the problem is going forward rapidly. 



