258 University of California Publications t?i Agricultural Sciences [Vol. 2 



SIMPLEX Z9 

 Plate 46, figure 1 



Simplex Z9 was isolated in 1920 from a stock originating from 

 seed collected at Quj^ Fen,- England. The original culture consisted 

 of plants ranging from entire to pinnatifid. The simplex Z9 race was 

 obtained by inbreeding plants with entire leaves. Although inbreed- 

 ing has reduced the amount of variation, there still appears in this 

 supposedly homozygous race a small percentage of semi-pinnatifid- 

 leaved plants (pi. 46, fig. 1). Anthocyanin and rib hairs are present. 



SCALAEIS e29 

 Plate 46, figure 2 



This race was isolated in 1919 from the Eureka stock of Crepis 

 which produced the viridis and the pallid races. Tt is characterized 

 chiefly by long, simple, pinnately-divided leaves with pointed lobes. 

 The terminal lobe is slender and elongated, often curved to one side 

 near the tip. Both anthocyanin and rib hairs are present. The 

 average number of lobes per leaf is 10. It is dominent when crossed 

 with simplex Z9 or with viridis. Typical leaves of the scalaris e29 

 and the simplex Z9 races are shown in plate 52, together with the 

 F^ and Fo types obtained when these two races are crossed. In the 

 Fj a few extreme variants occur which approach the simplex form, 

 but the majority are more nearly like the scalaris and constitute a 

 fairly uniform intermediate type. In the Fo, three types are dis- 

 tinguishable (see pi. 51, fig. 2), the two grandparental forms and an 

 intermediate scalaris form similar to the Fj. When the intermediate- 

 scalaris and the scalaris are grouped together a 3 to 1 ratio is obtained 

 (see table 6). The intermediate forms differ from the scalaris in 

 having the lobes less deeply incised, some more so than others, but 

 still classifiable as intermediate. (See third and fourth loaves in 

 F„ pi. 52.) 



From the results of breeding it appears that there is present one 

 main gene for lobing and that dominant modifying genes are involved 

 which act cumulatively, thus producing intermediates of different 

 grades of pinnate lobing. As a corollary to this hypothesis races 

 breeding true for different grades of intermediate pinnatifid lobing 

 should be possible. There is evidence that such races occur. Several 

 intermediate forms have been testerl and found to be fairlv constant. 



