492 University of California Fuhlications in Botany [Vol. 5 



The same quantitative factors that differentiate the narrow-leaved f orm^ 

 of SESSiLiFOLiA from the typical broad-leaved forms may apparently 

 differentiate narrow-leaved stenophylla, latifolia, and auriculata 

 forms from the more typical broad-leaved ones. It is of interest in 

 this connection to note that loriifolia derivatives have much narrower 

 leaves than either of the original parents. 



We have been especially interested in these loriifolia derivatives 

 because they are somewhat like the narrow-leaved forms that Hassel- 

 bring (1912) found among Cuban tobaccos, and which are so well 

 recognized among Cuban growers as to have received the specific desig- 

 nation of lengua de vaca or "cow's tongue." Our results indicate 

 that it is possible for such forms to arise by segregation from crosses 

 between broader leaved forms. The lengua de vaca of the Cuban 

 growers is, therefore, probably a segregation product which could 

 easily be eliminated by the adoption of proper pure line methods of 

 breeding, 



Auriculata forms appear to breed true whenever segregated. The 

 exception is type 8, which requires further investigation. It may be 

 a leaf type shnilar to auriculata but of different genetic constitution. 

 Auriculata of type 10 bred true in F,. The auriculata form 6a, 

 which segregated from type 6 bred true thereafter. Auricuuvta 

 crossed with macrophylla, H54, Hgg, H-^, and H-g, gave SESSiiiiFOLiA in 

 Fi and in F2 3 sessilifolia : 1 auriculata. 



Sessilifolia forms have broad sessile leaves, the distinguishing 

 feature being merely their sessile mode of attachment. Of such selec- 

 tions from the original ¥n populations, four, with the exception of one 

 anomalous plant, bred true for sessilifolia. Each of the other three 

 populations segregated into sessilifolia and auriculata in about the 

 ratio of 3 sessilifolia : 1 auriculata. Two sessilifolia selections 

 were grown in 1917. One of these bred true to sessilifolia ; the other 

 gave 3 sessilifolia : 1 auriculata. The behavior of sessilifolia in 

 relation to stenophylla and latifolia is explained above. 



On the basis of these results we may distinguish certain definite 

 allelomorphic pairs of factors as follows 



Ss, stenophylla versus sessilifolia : SS being long petioled like 

 angustifolia, and ss broadly sessile like macrophylla. The heterozygote 

 may possibly approach an intermediate condition similar to latifolia. 



LI, stenophylla versus latifolia: LL being long petioled like 

 angustifolia, and 11 short petioled like latifolia and with a distinct 

 but not broad wing. The contrast is really one of SSLL, stenophylla 



