114 HEREDITY AND EVOLUTION IN PLANTS 



ducing a "bud-sport" (Fig. 60). Such was the origin of 

 the seedless naval orange from the seed-bearing orange. 



91. The Evening-primrose. — In 1886 de Vries began to 

 search for a species that was in a mutating condition, be- 



FiG. sg. — Yellow daisy, or cone-flower {Rudbechia sp.), showing varia- 

 tions of the character of mutations in the ray- and disc flowers. At i 

 the normally ligulate corollas are tubular; at / they have all aborted, 

 except two; at h many of the normally tubular disc-flowers have become 

 ligulate, making a nearly "double flower." (Photo by E. M. Kittredge.) 



lieving that any given species is at some periods in its 

 history more labile or changeable than at other periods. 

 After a long search he found, in an abandoned potato field 

 at Hilversum, near Amsterdam, a large number of plants 

 of Lamarck's evening-primrose {(Enothera Lamarckiana) 

 (Fig. 61). 



