xvi Contents 



Lecture Page 



XVII. The production of double flowers . . 488 

 Sudden appearance of double flowers in 

 horticulture. Historical evidence. Ex- 

 perimental origin of Chrysanthemum 

 segetum plenum. Dependency upon 

 nourishment. Petalody of stamens. 



XVIII. New species of Oenothera .... 516 

 Mutations of Oenothera lamarokiana in 

 the wild state near Hilversum. New 

 varieties of O. laevifolia, O. brevistylis, 

 and 0. nanella. New elementary species, 

 O. gigas, 0. rubrinervis, albida, and ob- 

 longa. O. lata a pistillate form. In- 

 constancy of O. scintillans. 



XIX. Experimental pedigree-cultures . . . 547 

 Pedigree of the mutative products of 

 Oenothera lamarckiana in the Botan- 

 ical Garden at Amsterdam. Laws of 

 mutability. Sudden and repeated leaps 

 from, an unchanging main strain. Con- 

 stancy of the new forms. Mutations in 

 all directions. 



XX. Origin of wild species and varieties . . 576 

 Problems to solve. Capsella heegeri. 

 Oenothera biennis cruciata. Epilobium 

 hirsutum cruciatum. Hibiscus Mos- 

 cheutos. Purple beech. Monophyllous 

 strawberries. Chances of success with 

 new mutations. 



XXI. Mutations in horticulture .... 604 

 Chelidonium majus lacinatum. Dwarf and 

 spineless varieties. Laciniate leaves. 

 Monophyllous and broom-like varieties. 



