SPECIES HYBRIDIZATION 241 
sylvestris in all their characters. These latter plants are fertile and in 
succeeding generations give offspring which to all indications are pure 
sylvestris individuals. Similarly when pollen of the N. tabacum parent 
is used, the sesqui-hybrids are of a variety of forms, but all approximate 
Fia 104.—Nicotiana tabacum ‘‘Cuba”’ (left) and its Fi hybrid with N. sylvestris (right). 
(After Goodspeed and Clausen.) 
the N. tabacum parent in their characters and no one could determine by 
studying them that they were only once removed from N. sylvestris. Those 
which most closely approximated the N. tabacum parent in morphological 
characters are also most fertile and give rise to fertile races which do not 
differ significantly from the N. tabacum parent. 
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