studies of lamarckiana seeds and pollen grains reveal 

 a high percentage of sterility— 60% of the seeds and 50% of 

 the pollen grains— a characteristic of hybrids formed by 

 crossing distinct species. The fact that it ' produces differ- 

 ent kinds of fertile gametes every generation, and forms 

 twin hybrids in approximately equal numbers when crossed 

 with certain wild species, as do several of the wild species in 

 crosses with each other, ' ' shows that it has the variability 

 characteristic of hybrids." 



Fig. 11. — Lamarck's Evening I^rimrose 

 ("Oenotliera lamarckiana"). 



Examples of Mutations. — Weeping willow, nectarine, 

 Houghton and Downing gooseberries, garden strawberry, 

 purple leaved plum, Catawba, Concord and Clinton grapes, 

 Wilson's Early, Lawton, Wilson Junior and Eureka black- 

 berries, DeVries' species of Lamarck's Evening Primrose, 

 the peloric toad-flax, cockscomb, Shirley poppy, white 

 cyclamen, Burbank's lavender-scented dahlia, seedless 

 navel orange, moss roses, thornless cacti, seedless banana, 

 kohlrabi, cauliflower, red sunflower, sweet peas, Boston 



68 



