1924] Collins: Inheritance in Crepis capillaris (L.) Wallr. 267 



conditions which made accurate classification difficult and uncertain. 

 One F^ gave a 1 to 1 ratio and another the ratio 2 procumbent to 1 

 normal. 



EEECT (e) 

 Plate 50, figure 1 



A strain characterized by erect habit of growth, large stiff lateral 

 branches, and a thick rigid central axis. The branches make an acute 

 angle with the axis, the whole plant having the form of an inverted 

 cone. This form was selected from the F^ of a cross between the 

 Danish and Swedish stocks. 



PALE A (p) 

 Plate 51, figure 1 



The nature of this character has previously been discussed (Collins, 

 1921). It originally appeared in an F^ hybrid and was considered a 

 reversion to a possible, pre-composite, ancestral condition. It has 

 appeared in every case in hybrids, never in inbred races, and was 

 probably introduced with the Danish stock, since the same plant 

 (17.198P.) of that stock is in the pedigree of all the hybrids which 

 have produced palea. Races homozygous for palea have been 

 obtained. Preliminary data show palea to be conditioned by a single 

 recessive gene. 



Linkage 



In a species ha^dng only three pairs of chromosomes, it would 

 seem fairly easy to establish groups of linked genes, especially when 

 the species w^as known to be more or less polymorphic. However, it 

 has not yet been possible to realize this end, due to the unexpected 

 relations of some of the genes in this species. For instance, there 

 are four cases of complementary recessive genes, and three characters 

 dependent upon duplicate dominant genes. The determination of 

 linkage groups under such conditions is complicated because it re- 

 quires a longer time to obtain races with a known and tested genotype. 



The gene for bald involucre appears from data in tables 12 and 13 

 not to be linked with the gene for smooth ribs nor wath the gene for 

 procumbent, since the ratios show independent segregation. 



It is of course obvious that linkage must occur between one pair 

 of complementary genes for smooth ribs and one pair of complemen- 

 tary genes for revolute leaves, since there are four pairs of genes and 



