Varietäten, Descendenz, Hybriden. 3 



a recessive to the erect vexillum, but in certain strains in which 

 both red and purple flowered plants occur the hood is always asso- 

 ciated with the latter colour. In such cases it must be supposed that 

 all the "red" gametes bear the factor for the erect vexillum, and 

 that this factor is absent from all the gametes which carry purple. 

 It would seem therefore that the two dominant factors, blueness and 

 erect vexillum, repel one another in gametogenesis so that they are 

 not both found in the same gamete; consequently only two kinds ot 

 gamete are produced instead of the four characteristic of a normal 

 case of di-hybridism, and the result is a simple 1:2:1 ratio. Certain 

 consequences which should follow if this Interpretation is correct 

 have been tested by experiments (given in detail on p. 10, 14ahd 15 

 of the Report) and have been found to occur in accordance with ex- 

 pectations. The authors propose the term "spurious allelomorphism" 

 for the phenomenon. In other strains than those dealt with here 

 there exist red hooded forms with which experiments are now in 

 progress. 



Partial gametic coupling. 



Experiments further elucidating this phenomenon are recorded. 

 In the previous Report it was shown that the coloured offspring ot 

 plants heterozygous for blue factor and for long pollen could be 

 classified as purples and reds in the ratio 3:1, and as plants with 

 long and round pollen in the same ratio. The distribution of the 

 forms of pollen among the coloured plants was complex, but might 

 be explained by supposing that the majorit}'- of the gametes carrying 

 purple carried also the factor for long pollen, and that the cor- 

 responding majority of gametes from which the blue factor was 

 absent were also without the factor for long pollen. It was suggested 

 that the gametic series produced by the F x plant was of one of the 

 two forms: 



a. 8 purple-long, 1 purple-round, 1 red-long, 8 red round, 

 or b. 7 purple-long, 1 purple-round, 1 red-long, 7 red-round. 

 The numbers obtained during the past two j^ears are somewhat 

 more consistent with the scheme based on the 7:1:1:7 ratio. 



Two cases have now been found in which the coupling is of a 

 closer type, namely of the form: 



15 AB : 1 Ab: laß: 15 ab. 

 One of these cases has to do again with the factors for purple and 

 pollen shape (which thus show different degrees of coupling in diffe- 

 rent families), the other has to do with two different pairs of factors, 

 viz., dark and light axil, and fertile as opposed to sterile anthers. 



The gametic series resulting from partial coupling of the above 

 types may be expressed generally in the form 



(n— 1) AB : lAb : laß : (n — 1) ab, 

 and the offspring resulting from self-fertilization would be 



(3n 2 — (2n-l)) AB : (2n— 1) Ab : (2n— 1) aB : (n 2 — (2n — 1)) ab. 

 The authors point out that when n becomes very large this ap- 

 proximates to 



3n 2 :0:0:n 2 , 

 and thus when aberrant forms occur in a series which is apparently 

 of the usual 3:1 type, it may be worth while examining them 

 with a view to the possibility that they may represent the scarcer 

 terms in a series resulting from close coupling. 



The wild Sweet Pea. Plants raised from seed of the wild 

 Sicilian Sweet Pea proved to be, on the whole, very like the Purple 

 Invincible. Both light and dark axilled plants occurred. One of the 



