1924] Collina: Inheritance in Crepis capillaris (L.) TTallr. 265 



indicates that there may be duplicate genes for dwarf II ; sufficient 

 data are not at hand to establish the hypothesis. Culture 22.160 

 (from 21.99Pi-,, a normal plant) gave 84 normal plants. 



The yellow appearance of the leaves in dwarf II seems to be a 

 dominant character from its appearance in 22.407, F^ of the cross 

 22.169P.O X 22.26IP4, the male parent being a dwarf II plant from 

 a pure culture. Inasmuch as the F^ plants are not dwarfish, it appears 

 that the yellowing and dwarfing may be due to separate but probably 

 linked genes. All the dwarf II plants which have appeared were 

 yellowish, and we may therefore assume that, instead of linkage, 

 the appearance of dwarf II is dependent on the presence in the zygote 

 of the dominant gene causing yellowing. 



DWARF III (dlll) 

 Plate 49, figure 1 



This variation first appeared in 1919 culture e5. It reappeared in 

 1921 in a culture (21.76) which came from the same source as e5. 

 The ratio of normal to dwarf III in 21.76 was 15 to 1, and in the 

 progeny of 21.76?^ (culture 22.117) 3 to 1. (See table 10 for data.) 

 Dwarf III was at first called 'semi-lethal, ' because of the high mortality 

 in this class of plants. These plants remain very much smaller than 

 their normal sibs during the rosette stage and reach maturity much 

 later. A large percentage die after they have formed a rosette and 

 before they reach the flowering stage. 



This variation appeared in several members of the same stock 

 which produced revolute, viridis, and pallid. 



SPREADING (sp) 

 Plate 49, figure 2 



A lax, open-branching habit which appeared in 20.37, the French 

 stock of Crepis. The stems and branches are long and slender, appear- 

 ing to be so weak they cannot support themselves in upright position. 

 Dwarf II appeared in this race and all have this spreading habit. 

 Data from crosses (21.26 and 22.173, table 10) show that it is a reces- 

 sive character. When the same plant (2O.37P3) was crossed to another 

 erect plant (19.IIlPji), it behaved as a dominant (21.28, 22.41, and 

 22.43, table 10). Of the F, cultures, only 22.173 was grown under 

 desirable conditions ; the others were overcrowded in greenhouse and 

 lath house, which interfered with proper development of this char- 

 acter. 



