254 IJ7riversiiii of CaUfnrnia Piiblication/t in Agricultural Sciences [Vol. 2 



but in the oriji:inal records they were (lesi<j^nated as intermediates. 

 If the culture 20.141, containing the intermediate-bald plants, is 

 removed from the table, the remaining cultures give an exact ratio 

 of 3 glandular to 1 bald ; when the intermediates are classified as 

 bald, the deviation from a 3 to 1 ratio is less than the probable error. 

 The progeny of two bald and two glandular F. plants were grown. 

 Both of the former gave, as expected, only bald offspring, while the 

 two glandular ¥., plants produced both types in F3. 



The nature of the intermediate plants has not been definitely 

 determined. The selfed progeny from one plant (18.dlP-o) gave a 

 culture (20.55) of 18 bald, 3 intermediate, and 3 glandular plants. 

 That they were not due to the incomplete dominance of the hybrid 

 produced by crossing bald with glandular is certain, for in the F^ 

 cultures (table 2) all plants were fully glandular. Another inter- 

 mediate bald plant (22.153Pis) produced 5 glandular and 5 bald 

 plants from selfed seed but none that could be classified as inter- 

 mediate, 



SMOOTH MIDRIBS (s) 



The midribs of the rosette leaves usually have a hairy pubescence. 

 From sporadically appearing plants, races have been obtained which 

 do not show these rib hairs ; such plants have been designated • as 

 'smooth' (s). The F^ resulting from a cross between these two types 

 of plants were all rib-haired, and in the F. there appeared 556 rib- 

 haired to 40 smooth plants. This is approximately a 15 to 1 ratio 

 and suggests the operation of two independent genes, each producing 

 the same somatic effect. 



Duplicate genes are by no means unknown, having been reported 

 a number of times in the literature of genetics. If two independent 

 genes w^ere operating in the cultures 21.140 and 21.141, the F, of 

 this same cross when backcrossed to smooth should give a 3S to Is 

 ratio and some F^ populations should give a 3 to 1 segregation. 

 Evidence from cultures of these two types has been obtained ; the 

 data from them together with data from other crosses involving this 

 character are given in table 5. The F., culture 21.189 was grown from 

 one plant of an Fo culture containing 58 rib-haired and no smooth 

 plants. Such a deviation is, however, only three times the probable 

 error and may well be due to errors of random sampling. The culture 

 F, 19. HI was originally made to determine the relation of the gene 

 for bald of the English race of Crepis to that in the Danish race and 



