392 



SCIENCE 



[Vol. LVI, No. 1449 



known, svispected, or yet to be discovered "in 

 the internal environment." 

 Yale University Yaxdell Hendek.son 



SPECIAL ARTICLES 



A CASE OF DUPLICATE GENES IN CREPIS 

 CAPILLARIS (L.) WALLR. 



The rosette leaves of Crepis capillaris (L.) 

 Wallr. noi-maJly have a more or less pronounced 

 pubescence on the lower surface of the 

 midrib. Often the upper surface is also sim- 

 ilarly pubescent, but not by any means in all 

 cases, and the sig-nificance of this latter differ- 

 ence, if any exists, has not been learned.' 



In 1918 in a culture which had its origin 

 from wild plants growing in Berkeley there 

 wa^ found a plant (17.192P.,) which did not 

 show the pubescence on the lower surface 

 of the midribs of the rosette leaves. When 

 selfed this plant reproduced the type and a 

 strain of "smooth" leaved plants was estab- 

 lished. Althougih there is some variation, in 

 the amount of pubescence on the libs of dif- 

 ferent plants of the hairy strain, there is no 

 diiiiculty in distinguishing the two groups. 



Crosses between these races at first gave dis- 

 cordant results. More recently with larger 

 cultures and perfected technique data have 

 been collected which indicate that hairiness of 

 the midribs is due to duplicate dominant genes, 

 which are not in the same chromosome group. 



Two F., cultures in 1921 gave 556 hairy- to 

 40 smooth-leaved plants, a rato of 14.926 to 

 1.073 ± 0.106, which is a very good fit indeed. 

 Among the F„ plants there should be an equal 

 number gi\'ing segregating populations and 

 populations containing only one type of plant. 

 Among those segregating in F, half should give 

 15 : 1 ratios and half 3 : 1 ratios. 



Data from F3 populations are not yet com- 

 plete but cultures giving both 3 : 1 and 15 : 1 

 ratios have been obtained from another cross. 

 These results show that the hairy plant used 

 as pollen parent in this ease was AABb which 

 gave all hairy in Fj^ and equal numbers of 3 : 1 

 and 15 : 1 populations in F,. This supplies 

 also the necessary data to satisfy theoretical 

 requirements for the duplicate geue interpre- 

 tation. 



Complete data from crosses involving hairy 

 and smooth characters are reserved for a futui-e 

 publication. 



E. B. Babcock 



j. l. collixs 

 Eerkelet, California 



INHERITANCE OF GLANDULAR PUBES- 

 CENCE IN CREPIS CAPILLARIS 

 (L.) WALLR. 



The usual wild t^^pe of this species has 

 glandular pubescence on the involucral bracts 

 and extending downward on the pedicel for 

 some distance from the flower head. 



In 1918 a single plant appeared which did 

 not have these glandular hairs. Such plants 

 have been designated as "bald." The culture 

 in which this "bald" plant appeared grew from 

 seed sent us from Copenhagen, Denmark. Since 

 this first appearance, "bald" plants have 'been 

 found in cultures derived from five other geo- 

 graphical locations as follows : England, Swe- 

 den, Chile, France and the Azores Islands. 



The identity of the gene in all the cultures 

 except that from France has been established 

 by crossing, which in all cases produced only 

 "bald" plants. 



The bald character is produced by a single 

 recessive gene. The F^ plants obtained from 

 crossing bald with glandular were completely 

 glandular. In a culture of 77 back crossed 

 plants 39 were glandular and 38 bald. A total 

 of 210 F., plants gave a segregation of 174 

 glandular to 36 bald, the ratio being 

 3.314 : 0.eS5. The deviation in this case is 

 3.89 times the probable error. The major part 

 of this deviation is due to one culture which 

 produced 72 glandular to 2 bald plants. When 

 this culture is excluded from the totals, there 

 then remains 102 glandular to 34 bald, which 

 is an exact 3 : 1 ratio. The F, bald plants 

 which were tested bred true in F^. Only two 

 glandular F., plants have been tested, 'Ixjth seg- 

 regating in F„. 



Detailed data for all bald cultures will -be 

 given in a future publication. 



E. B. Babcock: 



J. L. COLLISS 

 BeBKELET, CALIPORXLi. 



